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SY99 Music Synthesizer FAQ

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Part Two: SY99 Hardware

2.1. Internal Backup Battery

*Q2100: Information about the internal battery

To keep non-volatile memory alive, your SY99 is equiped with an internal backup battery.


*Q2101: Warning Message "Change internal battery!"

If the Warning Message 'Change internal battery!' appears when turning the SY99 off, call a local Yamaha vendor to replace the battery. It is highly recommended that you store a complete ALL backup on floppy diskette.


*Q2102: Battery lifetime

The lifetime of the internal backup battery is told to be more or less five years. It is said that the internal battery is being regenerated, when the SY99 is powered on. This would mean, that if you use your SY99 frequently, your battery might have a longer livetime. But maybe it's just the other way round. We are not sure on this.


*Q2103: Battery replacement

You can not replace the internal battery on your own. Call Yamaha Corp. for battery replacement.


2.2. Main and Sequencer ROM

*Q2200: Different ROM versions

The SY99 seems to have two ROM (Read-Only Memory) circuits, where the 'operating system' of the SY99 is located. Information stored in ROM circuits is always non-volatile. Depending on the circuit architecture, ROM memory can not be written.


*Q2201: Determining the ROM version of your SY99

You can determine the ROM Version of your SY99 by pressing the following keystroke sequence:


The Main ROM and SEQ.ROM versions will appear on the LCD Display. Press [EXIT] to leave the ROM information display. To update your SY99 ROM, contact Yamaha for replacement.

Please contribute your unlisted SY99 ROM versions (and date) to the FAQ maintainer


*Q2202: Main ROM versions

The following Main ROM versions are known (Year - Month - Day):

Version 1.13 1991-05-28
Version 1.24 1991-07-09
Version 1.33 1991-08-21
Version 1.40 1991-09-25
Version 1.57 1992-05-12


*Q2203: SEQ. ROM versions

The following SEQ. ROM versions are known (Year - Month - Day):

Version 1.10 1991-05-22
Version 1.20 1991-06-22
Version 1.30



2.3. Built-in Memory

*Q2300: Built-in Memory

The SY99 comes with 512K (1K=1024 bytes) buit-in Sample RAM (Random Access Memory). This basic memory can be used to hold samples and/or MDR data.


*Q2301: Volatile and non-volatile memory

Information stored in volatile memory will be lost when turning SY99 off, whereas data stored in non-volatile memory will be kept alive by the internal backup battery.


*Q2302: Saving Sample RAM

Samples require less sample memory if they are received via MIDI wire using the MIDI Sample Dump Standard (SDS, “Bulk Dump” feature). Saving and loading samples to a 3½” DD diskette will result in a bigger sample size.

Some people say, that it is best to initalize the Sample RAM from time to time, to prevent RAM fragmentation. We couldn'tt prove this, but it won't hurt. Maybe it is best to Initialize the Sample RAM whenever you delete your last sample.



2.4. Memory Expansions

*Q2400: Memory Expansions

There are several ways to increase the SY99 memory:

  • SYEMB Memory Expansion (Q2410)
  • MCD64 Memory Card (Q2420)


*Q2410: SYEMB Memory Expansions

Up to five SYEMB-05 Memory Expansion Boards may be installed to increase the amount of available Sample RAM / MDR RAM. SYEMB Memory Expansions are designed to be very user-friendly.

To install the memory expansions, remove the "SY99" labeled cover on the rear side of your SY99. Follow the instruction manual included with the memory expansion board to upgrade your internal RAM. The amount of MDR value can in no way exceed 512K.

SYEMB Memory Expansions 
MDR size 
sample size 
none (only basic 512K RAM)
none (only basic 512K RAM) 
  0 K
512 K 
  512 K
    0 K 
1 (basic 512 K + 512 K)
1 (basic 512 K + 512 K) 
  0 K
512 K 
1.024 K
  512 K 
2 (basic 512 K + 1.024 K)
2 (basic 512 K + 1.024 K) 
  0 K
512 K 
1.536 K
1.024 K 
3 (basic 512 K + 1.536 K)
3 (basic 512 K + 1.536 K) 
  0 K
512 K 
2.048 K
1.536 K 
4 (basic 512 K + 2.048 K)
4 (basic 512 K + 2.048 K) 
  0 K
512 K 
2.560 K
2.048 K 
5 (basic 512 K + 2.560 K)
5 (basic 512 K + 2.560 K) 
  0 K
512 K 
3.072 K
2.560 K 


*Q2411: SYEMB Memory Expansion Types

Type may be used with
SY-EMB05 SY-99
SY-EMB06 SY-85, TG-500, RY-20, maybe RM-50

If your unlisted synthesizer supports SYEMB memory expansions, please submit name and manufacturer of your synth to the FAQ maintainer


*Q2420: MCD64 Memory Card

Generelly, MCD64 Memory Cards are RAM cards that can be used to store patches, multi setups, synth setup, sequencer data or other type of user data. MCD-64 Memory Cards may be used by different synthesizers (see incomplete list below).

For the SY99 (and probably the SY77 / TG77 too) you can only store one patch bank (Card) or other types of synth data. Other SY- and TG-synths (such as the 22 / 33 / 35 / 55 series) will save two patch banks )

It is said that the MCD-64 stores up to 64 KByte whereas the MCD-32 stores only 32 KByte of data.

The MCD-32 Memory Card is NOT compatible with the SY99.


*Q2421: MCD Memory Card Types

The following table might give you a first impression about possible combinations between MCD Memory Cards and synthesizers:

Card Type may be used with
MCD-32 SY-22, TG-33, SY-35, SY-55, TG-55, YS-100, V-50, B-200, RX-8
MCD-64 SY-99, V-50, some other synths of the SY- / TG- / RM series

If your unlisted synthesizer supports MCD Memory Cards, please submit name and manufacturer of your synth to the FAQ Maintainer


*Q2430: Missing SIMM support

Unlike the Yamaha SY85 Synthesizer, the SY99 does not seem to handle single inline memory modules (usually referred to as 'SIMM').

It is said that the SY85 can handle 30pin / no-parity / 80ns SIMMs. If you have an SY85, make sure you reinitialize the memory of your SY85 after SIMM installation, otherwise the RAM may not be accessed.


*Q2440: Third Party Memory Expansions

There has been mentioned a board from Musitronics somewhere in Germany which will allow the SY99 to have 8MB sample RAM, but noone is sure how well it works.

If anybody is using the Musitronics board, please let us know how good it is, where you got it and what you paid for it.

Unfortunately, no other company except YAMAHA sells memory expansions for the SY99 Music Synthesizer. If you know a memory expansion solution not mentioned in this FAQ, please drop a mail to the FAQ maintainer.


2.5. LCD Display

Most of the topics discussed here was cut & pasted while following a discussion between Don, Ola, Tom and Ton. Thanks for your efforts!


*Q2500: LCD Display

Your SY99 Music Synthesizer is equiped with a 240x64 pixel Liquid Crystal Display (LCD) with backlight for better readability.


*Q2501: Old displays

It is difficult to observe, but some people think, that old LCD displays get darker with the years.
Current theory is that this has something to do with the internal lamp getting weaker.

*Q2502: Display Replacement

Contact Yamaha for LCDDisplay Replacement.


*Q2510: Contrast Settings

See your SY99 manual to adjust the settings of the LCD contrast.



2.6. Floppy Drive

*Q2600: Floppy drive

Your SY99 is equiped with a 3½" Double Density MSX-type Disk Drive. This drive supports common 3½" DD floppy diskettes. MSX is an old 8 bit computer standard and this drive type was also used in older Yamaha music computers. Some people say, that MSX used 3" rather than 3½" drives. However, we claim that the only disk drive that can be used with the SY99/77 is the drive manufactured directly by YAMAHA.

Make sure you protect the disk drive when shipping or flying your synthesizer.


*Q2610: Do not use 3½" HD diskettes

Never use High Density (HD) or Extra High Density (EHD) disks with your synthesizer. You might encounter severe problems when re-using these diskettes on other computer systems (e.g. read fault errors or data errors).


*Q2611: Missing directory support

Do NOT use directories (folders) when storing data on your diskette. Sub-directories may NOT be accessed within the SY99.


*Q2612: Proper file handling

Files are recognized by their extensions. File extensions can have up to three alphanumeric letters. Each file extension has a different meaning. You can store up to 99 files per file type. For compatibility reasons, file names should only consist of uppercase letters and should not contain special characters.

If two files have exactly the same file extension only the first one will be shown when browsing the diskette with your synthesizer. You may access the second one by renaming or deleting the first file.

The appendix of the SY99 Operating Manual contains a list of supported file extensions.


*Q2613: Read-only file attribute ignored !

Don't trust on ATTRIB read-only settings when storing files on a diskette. The SY99 will overwrite both software-protected and not-protected files. If you want to go sure, apply the 3½” “hardware” write-protection.


*Q2620: Floppy drive replacement

If your disk drive got damaged, contact Yamaha Corp for replacement. You can not use standard 3½" disk drives (used e.g. with PC or Macintosh), as they are NOT compatible with the SY99 floppy disk controller. One of the main reasons might be the different data transfer speed (1,44M disk drives are much faster than 720K disk drives). Another topic to mention is, that if a controller supports multiple types of diskette drives, there should be a switch (DIP, jumper, BIOS setting) to select the appropriate drive type.

Due to this, the internal SY99 floppy drive cannot be upgraded e.g. to support 1,44M HD (high density) or 2,88M EHD (extra high density) floppy diskettes.


*Q2630: Increasing the drive speed

If you format your disk using the SY99 instead of using a standard PC or a Macintosh, disk access is said to be faster because of better interleave settings. However, we think that the disk drive is still very slow. Do diskettes really have an interleave at all ? We don't think so. If you know a way to accelerate the floppy, don't hesitate and share your experience.


*Q2640: Beware of SY99 autoformat !

SY99 may format your 3½” floppy disk automatically, without asking you for permission!

This happens if your SAVE ALL operation flows to the second disk, and the second disk is not empty. After inserting the 2nd disk and answering 'yes' to the question requesting for it ... whang bang ... it is nice to watch the extinction of your 2 weeks work!

This side-effect will not arise if you do not have memory expansions installed, as your data will thus never ever overflow to a second disk when storing an ALL DATA backup.


2.7. Sequencer

Sorry --- this part is currently under construction.

2.8. SY99 Internals

*Q2800: SY99 Internals

While the previous articles were about user elements, this chapter will give you information about real SY99 internals. This whole chapter deserves credits to Ola Löfberg (


*Q2810: Integrated Circuits

The following list will decode the numbers of Integrated Circuits (IC):

IC 101Sequencer ROM
IC 111 Main ROM: Program ROM
IC 112 Main ROM: Voice ROM (probably not the samples)
IC 113 Main ROM: Library ROM
IC 128 CPU (Central Processing Unit)
List of integrated circuits located on the SY99 motherboard.

If you know other codes, please submit them to the FAQ maintainer


*Q2820: Updating the Main ROM

The ROM-chips are ordinary 27C1001 EPROMs. They might be read/written with an EPROM reader/writer, if you have on handy. If not, contacting Yamaha might not be a bad idea.


*Q2821: Updating Main ROM Versions 1.xx to Version 1.3

When upgrading the Main ROM from an earlier version to Version 1.3 (or later), one (or both) SY99 CPUs may need to be replaced too (not sure on this).

Both CPUs are appearantly in socket and surface-mounted.


*Q2830: ROM-Fixes

  • VOICE-rom v1.1 to v1.2
  • Seq-ROM v1.1 to v1.2

CPU change to v1.3 and program-rom (ROM1 v1.3, IC111) should be replaced simultaneously.

During multi edit voice setting of some voices that use the waveform card, more than 2 kinds are assigned. When multi is stored or selected, "ERROR: ID number mismatch!" will be displayed on the LCD display.

When loading one sample data file from a disk, it is possible, in some cases, to load data in exess of the memory size set with the allocation function. This will disable the function to save and load data (ALL DATA) to disk

When MDR memory size is allocated 512Kbytes, and you execute the data input, the data is recieved even if the "memory full" error-message is displayed. However, the data cannot be saved to a disk. (Impossible with both MDR&DISK ALL DATA utilities)

If the "Vol-Low-Limit" setting is assigned to a a controller in the controller set function (DP228) and the controller is moved, the "EFFECT CONTROL" function (DP218) produces an error.


Voice ROM v1.1 to v1.2

In Voice ROM version v1.1 were spelling errors in the preset multi names:

P-14 Wind Ensemble / Ensemble
P-15 Ethnican / Ethnic
P-16 Folk

Voice ROM (ROM2 v1.2, IC112), Library ROM (ROM3 v1.2, IC113) and SEQ. ROM (v1.2, IC101) can be upgraded separately.


Seq-ROM v1.1 to v1.2 :

During Pattern (PTN) recording, "PTN REC CANCEL" (SHIFT+STOP)-function does not work with one of the mode buttons pressed (VOICE,MULTI and UTILITY).


CPU change to v1.4 and program-rom (ROM1 v1.4, IC111) should be replaced simultaneously.

AWM sound source sometimes does not perform when the voice is set at "AFM+AWM". (For example, sometimes the sound (with multi-timbre) is not generated, in spite of the existence of note data. This is because the sound wasn't generated in the original voice, due to a defect in the AWM sound source composing the voice of the part.)

LPF (parameter 10) set value of "Effect type 61,62,63" (mod & dly system) is not properly set when MIDI program change is recieved. Although the proper numerical value is displayed, the effect sound is not generated properly.

When changing the initial Delay (parameter 05) of "Effect type 14,15" (Gate Rev type), Rev Type (Parameter 01) becomes other than Gate Rev. Although the proper numeral value is displayed, the effect sound is not generated properly.

With the MDR function off, use the disk function to load a 702Kbyte data file. Next, the data is input with the MDR function, after which the data cannot be saved to the disk.


CPU change to v1.5 and program-rom (ROM1 v1.5, IC111, not an EPROM this time) should be replaced simultaneously.

When saved by the disk save function as ALL SAVE, including sample data, saving is finished using only one disk, although the data amount requires multiple disks. The sample data is lost.

Data disk (sample data) for TX16W is loaded into the main unit and saved to another disk as ALL SAVE. When loading from the disk, an error display appears and loading is not possible.

When MIDI reception channel is set to 2-16 (exept for 1) in voice mode, Bank select data cannot be accepted.

When the power is turned on in a low temperature enviroment, noise is generated occasionaly. However, if the effect bypass is on, the noise will not occur.

Noise occurs in some cases when Effect Parameter is changed while playing the keys in Effect edit. (Example: EFF1 No.45 has been changed to 40 and EFF2 No.5 has been changed to 24, and the EFF1: REV INIT DELAY value is being changed.)


Seq-ROM v1.2 to v1.3 :

When the entire length of a pattern was set for pattern-record and realtime recording (so it was not affected by the quantize value), it sometimes performed incorrectly and became impossible to operate.

Example: 3/16 time, measure 1, quantize 1/4. 1/4 time, measure 1, quantize 1/2.

Therefore, if the above settings were used, the quantize value was automatically decreased and made recording possible.

Only Seq-ROM can be upgraded here...


*Q2840: SY99 Bugs

Some strange behaviour your SY99 synth might show up one fine day:

  • I experimented a bit with the SY99 sample engine (using Avalon, a sample processing software for the Atari ST), and found out, that the 99 can only use the start/attack phase and the loop phase of samples, It never (?) plays any samples behind the loop phase, like one would expect.
  • Another strange thing is that if you use a very short low tuned sample and play a high note, the sample engine does miss the loop end and starts to play back the whole internal sample memory (including all the ROM waves). Besides the fact that this is obviously a bug, its nice hearing the ROM in fast forward mode ...
  • I always had problems with my SY-99 doing MIDI-SDS (sample dump):
    - the end of the sample somtimes seems to get lost -> wrong looping
    - I did successfully circumvent this problem by putting some useless samples behind the end of
    the sustain loop. (My guess is that the last SDS block is lost in some cases.)
  • In an old KEYS (German keyboard mag) I found a little note that the ROM version 1.40 is buggy and having this (and only this) version might be a reason to change ROMs to avoid problems with the sample RAM expansion.
  • Effect-unit can freak out when doing program change while playing on the keys.
  • When you have a disk with an ALL-file on and you want to overwrite it with a newer one, you can't overwrite if the disk doesn't have enough free space to contain both at the same time. (you'll simply first have to delete it and then save the new one with the same name.
  • I have an SY99 and I have noticed that when I load multi's, ALL data, synth daya, etc., from disk, a wierd thing happens. I don't know if it is ALL of the time, but it is certainly often enough for me to have trouble with this. After I load on of these things, and I go to [MULTI], "EDIT VOICE", (PAGE 401 on the top right of the LCD screen) the voice in the 1st channel of the 16 available in the multi, will play even if I am not on that channel. For example:

    Lets say I have just FACTORY RESET the SY99. The first multi is POPULAR. In that multi are 16 voices, the 1st being EP|GrnDual. The 5th is PL:Echoes6, the 11th is CH:Itopian. I have given these examples as random choices that are ACTUALLY programmed in the DEFAULT settings so we are all on the same "track". Anyway, If you choose [MULTI], EDIT - VOICE, you will be able to curser to any of these voices and play them on the keyboard, you can edit each individual voice, etc. from here. Each voice should play seperately, Right??? Well in this situation, it will (after a FACTORY RESET). If I then load something from disk, and repeat the steps to do a MULTI - EDIT - VOICE, then curser to any given voice that is there(except the voice that is in position 1), the voice that is in position 1 and the voice that is highlighted by the curser will play at the same time. It doesn't matter which voice the curser is on. I still get the #1 voice playing with the voice where the curser is actually on. If I turn OFF the voice in the #1 position, then everything else is fine.

    I hope that my explanation was at least somewhat clear. Can someone help me with this problem??? I realize that there must be some instruction on the disk that is telling the SY99 to do this. Just in case it is pertinent, I have the SY99 connected to a computer using Cakewalk ProAudio. Please help me...I can't edit my multi's properly when this happens. Thank you for time and consideration.
    (posted by Steven)

    Are you sure you have not a software midi thru on into your PC? Did you try disconnecting midi from SY99?
    (answer by Stefano)

    I will bet that you have your 99 midi out somehow coming back to your midi in. (maybe through an external sequencer or something).
    Try this . When you get the problem happening that you describe, go to the midi transmit channel in the SY (page 807) Change the midi transmit channel and the voice that is being triggered (the one one that should not be triggered) will change to another voice . The solution is to try working with your setup with LOCAL OFF(also on page 807).

    Another thought is that you may have have a master setup selected. Turn it off.
    (answer by Paul)

    In the end, set your cakewalk channel to what channel you wish to fuck with on the sy99. make sure you have your main midi channel set to the corresponding midi channel you have set to record on cakewalk (ie. check your edit event in cakewalk to actually vericy youve recorded the correct midi channel).

    You must also set the local off on SY99, otherwise each note is played two times, one from SY99 keyboard, one from PC.
    (answers by Joy / Stefano)

  • If you discovered another bug or if you can prove one of those mentioned above, please submit your Name, your Email address and - most of all - your ROM versions to the FAQ maintainer

2.9. Front Panel

*Q2900: Front Panel

Your SY99 comes with a front panel. Select "Switch Lock" to disable your front panel: [Utility], "F1: Sys", "Switch Lock".


*Q2910: Undocumented Keystrokes

The SY99 has some tricky keystrokes to enter special features:

  • ROM version information display (Q2201)
  • SY99 Test mode (Q2911)
  • SY99 Debug mode (Q2912)
  • Changing main volume bahviour (Q2913)


*Q2911: SY99 Test Mode

The SY99 Test Mode was designed to test the SY99 hardware components.

Aside the normal SY99 Test Mode, there is an even more hidden “Advanced SY99 Test Mode”, which can be accessed by pressing [1] or [2] from the SY99 Test Mode main screen (see below).

CAUTION: Do NOT use the SY99 Test Mode if your synthesizer is working properly.
When entering SY99 Test Mode, you will loose all non-saved edit information stored
in volatile memory (e.g. the complete sequencer memory contents), since SY99 Test Mode
can only be exited by rebooting the SY99 (by turning off and turning it on again).

Therefore, it is highly recommended that you make a complete backup of your SY99 memory before entering SY99 test mode.

Diskette test routines may overwrite / format / erase disk contents. Insert a special test diskette with non-sensitive data before testing the disk drive.

Also dettach other synthesizers and amplifiers, because some low level test routines may send a maximum velocity sine tone to the output groups. These test routines can destroy your monitor equipment.

Enter the SY99 Test Mode by pressing (and holding down) [Voice]-[Bank D/EL4]-[8/OP 8]

Once entered, follow the on-screen instructions:

*** SY99 TEST Ver 1.10 *** Please select 
 Main ROM : Version 1.57 1992-05-12
 SEQ. ROM : Version 1.20 1991-06-22 
   [-1] : Auto        [+1] : MANUAL
 [COPY] : Fact.Set  [EXIT] : Exit 

Now press one of the following front panel switches:

-1 / NO] Auto mode, all tests will proceed automatically, beginning with test #01
[+1 / YES] Manual mode, manually select which test(s) shall be executed.
[COPY] Return to FACTORY PRESET settings.CAREFUL: This will erase all memory contents.
[EXIT] Exit / Restart without testing.
[1] Additional test for DSP (20bits).

CAUTION: This will produce high-velocity output. Dettach your monitor equipment before executing this test.

[2] Additional test for WAVE-RAM. Executing this test may take several minutes.

Your SY99 MIDI Manual shows a way to enable this test mode by sending the System Exclusive Message F0 43 1n 18 5A 00 F7 to your synthesizer (where n is probably the device number).


*Q2912: SY99 Debug mode

The SY99 has 11 different debug modes. You can access each debug mode by pressing (and holding down) the 'debug mode switch sequence' ( [Cursor Left]-[Cursor Right]-[Cursor Down]) in combination with one of the following keys:


Pressing [Left]-[Right]-[Down]-[Enter] will show a short information display about all available 'undocumented' keystrokes:

[0] task LED
kill cntrl
init ram$
xmit kas out
ch LED
kill ad_scan
xmit seq prm
show title
bye bye
xmit screen



[0] task LED

This operation is being investigated. If you have any further knowledge about this feature, please mail to

According to the task (?) management, the 8 LEDs (4 Memory and 4 Bank) on the upper right corner will lighten up.


[1] kill cntrl

This operation is being investigated. If you have any further knowledge about this feature, please mail to

This might be some kind of MIDI 'panic' button, e.g. when a MIDI controller 'hangs'.


[2] init ram$...


This keystroke sequence will ERASE ALL MEMORY CONTENTS and
load FACTORY PRESETS. Your SY99 will then be rebooted.


[3] xmit kas out

This operation is being investigated. If you have any further knowledge about this feature, please mail to


[4] ch LED

This key command sequence will enable the 'channel mode'

[EF BYPASS]-LED becomes a MIDI OUT status LED. Each time a note is played or released, the LED status will be set to on.The 16 Operator LEDs will show the internal voice organisation.

Pressing the whole sequence again will turn this option off.


[5] kill ad_scan

This operation is being investigated. If you have any further knowledge about this feature, please mail to


[6] xmit seq prm

This operation is being investigated. If you have any further knowledge about this feature, please mail to


[7] designers

The designers screen will show you the names of the SY99 designers: 
| SY99 Designers                        |
|                                       |
|                                       |
| Thanks for all designers of SY77      | 

The designers screen will disappear automatically after five seconds.


[8] show title

This will restart your SY99. It has the same function as if turning the SY99 off and on again.

You will loose all data stored in volatile memory (e.g. sequencer contents and non-saved
edit changes) when executing this command.


[9] bye bye


This operation will erase data stored in volatile memory and lock your synthesizer.

This will produce the following message on the LCD screen:

| Sorry!                          |
| Error occured. (*****)          |
| Please turn the power off once. | 

The (*****) usually referrs to as the error number. To exit this display, turn power off and on again.


[-] xmit screen

This operation is being investigated. If you have any further knowledge about this feature, please mail to


*Q2913: Changing the Main Volume Fader Behaviour

When pressing [SHIFT]-[EF BYPASS], the Main Volume Fader will change its behaviour and directly affect the Wet/Dry of the Effect Processors instead of controlling the Main Volume.

When entering this 'direct effect control' mode, the [EF BYPASS]-LED will start to blink.

By pressing [EF BYPASS] the original behaviour of the Main Volume Faders is restored.


Intro Hardware Howto Stuff Reference

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