Yamaha YRM-502
This page was last modified 18:17, 7 December 2021 by Mars2000you. Based on work by Gdx and Rderooy and others.



The YRM-502 (YRM-55 in Japan) FM Voicing Program II is the second version of the software developed by Yamaha to give precise control over the SFG digital FM voice generator. This software, released in 1985, was sold on cartridge, but it was also pre-installed into the MSX1 CX5MII and the MSX2 CX7M/128 computers as a mini-cartridge. It allows to modify the pre-programmed voices 1 to 48 and create entirely new voices from scratch.

All data can be saved on disk, cassette tape or data memory cartridge UDC-01. The data and the list of all voices can also be printed (hardcopy of the screen).

Contrary to the 1st version, the software is not launched automatically after booting. You need to enter CALL FMV or _FMV.


YRM-502 Command menu

The YRM-502 software displays 7 main screens: the Command menu on which you land after the intro screen, the Directory (enter DI on the command line), the Edit mode that you can reach by pressing F1, the Load/Save menu (enter TR on the command line) and 3 different Key lists, accessible by pressing F5, for the Command, Edit and Load/Save modes.

The command line is available on all screens, except the Key lists. In the Edit mode, you need to press F1 to switch between this line and a block. The main commands can't be entered on the Load/Save menu screen, while the specific Load/Save commands are only available on this special screen.

The green point on the line under the command line indicates the split point of the music keyboard between instrument 1 used in polyphonic mode for the editing keyboard and instrument 2 used in monophonic mode for the comparison keyboard. By default, this point is set at the lowest key, so it means that all keys are used for the editing keyboard.

To change the split point, you need to press SELECT, then a key on the music keyboard. The keys at the left of the green point will be used for the comparison keyboard. The current voice data are set for this keyboard by pressing F4 in the Edit mode.

Command menu (HE)

The screen of the Command menu is divided into 3 parts: a command line on which you can enter different commands, the list of the main available commands and the explanation of some abbreviations. Voice number can vary between 1 and 48.

Command Meaning
n voice number n Select voice n and go to Edit mode
CO n, m COPY voice number n, voice number m Copy data of voice n to voice m
DI DIRECTORY Go to the Directory screen
HE HELP Back to Command menu
KI n KILL voice number n Initialize voice n to create a new voice from scratch (original data are saved in the save buffer)
MU MUSIC Go to the SFG-01 or SFG-05 synthesizer firmware
PR n, m PRINT voice number n, voice number m Print the data for voices n to m (hardcopy of screens)
RE RESTORE Replace the data of the currently edited voice by the data saved in the save buffer
RE n RESTORE voice number n Replace the data of voice n by the data saved in the save buffer
SA SAVE Save the data of the currently edited voice in the save buffer
SA n SAVE voice number n Save the data of voice n in the save buffer
SP a SELECT PRINTER a Select printer type (a=1 for MSX, 2 for EPSON)
SW n, m SWAP voice number n, voice number m Swap data of voices n and m
TR TRANSMISSION OF DATA Go to the Load/Save menu

Directory (DI)

YRM-502 Directory

The screen of the Directory is divided between the command line and a list of all of the names and numbers of the voices stored in the computer memory. By default, it's the list of the system voices.

This list can be different after loading of created voices from disk, cassette tape or data memory cartridge, or switching to user voices in the SFG-05 firmware.

Access to the SFG-01 or SFG-05 firmware is indeed possible, by entering MU on the command line; you can then press twice on SELECT to switch between the system voices and the user voices if you are using the SFG-05 module. To go back to the FM Voicing Program, you need to press ESC in the synthesizer firmware.

Edit mode (F1)

YRM-502 Edit mode (F1)

The screen of the Edit mode is divided between the command line (access by pressing F1) and 5 blocks allowing to make a fine editing of the currently displayed voice.

General settings are in the first block, specific settings for each operator of the digital FM voice generator are in the 4 blocks with number 1 to 4. The cursors are useful for selecting a parameter. To modify it, just type the new value and press RETURN, or use the (INS +) HOME or DEL keys.

Each of the 4 operators can be switched ON/OFF by pressing CTRL + one of the keys 1 to 4 corresponding to this operator. You can also move the cursor over the operator number and type in a different number to turn it OFF or the correct number to turn it ON. Instead of typing a number, you can also use the HOME and DEL keys.

General settings

Parameter Values
Code Personal code as memo for selecting a voice 0 to 99
Tr Transpose -128 to 127
LR Left Right Switch 00 (no output), 10 (left channel), 01 (right channel), 11 (both channels)
Ams Amplitude Modulation Sensitivity 0 to 3
Pms Pitch Modulation Sensitivity 0 to 7
Name Voice name Use BS for corrections before pressing RETURN !
Al Algorithm 1 to 8
Fb Feedback (operator 1) 0 to 7
Ne Noise Enable 0 (OFF, then change the keyboard split point) or 1 (ON)
Nf Noise Frequency 0 to 31 (press F4 after each change)
LFO Low Frequency Oscillator 0 (OFF) or 1 (ON)
Syc Synchronization of LFO to the playing of a note 0 (OFF) or 1 (ON)
Wf Waveform 0 (sawtooth), 1 (square), 2 (triangle), 3 (sample & hold)
Spd Speed (LFO frequency) 0 to 255
Amd Amplitude Modulation Depth (LFO influence on volume) 0 to 127
Pmd Pitch Modulation Depth (LFO influence on pitch) 0 to 127

Specific settings for each operator

Parameter Values Parameter Values
A Envelope generator - Attack Rate 0 to 31 IF Inharmonic Frequency 0 to 3
D Envelope generator - 1st Decay Rate 0 to 31 Dt Detune -3 to 3
S Envelope generator - Sustain Level 0 to 15 Ks Key Scaling Select 0 to 3
D Envelope generator - 2nd Decay Rate 0 to 31 Kd Key Scaling Depth 0 to 15
R Envelope generator - Release Rate 0 to 15 Rk Rate Key Scaling Depth 0 to 3
O Output Level 0 to 127 Vs Velocity Sensitivity 0 to 7
F Frequency 0 to 15 Aj Adjust 0 to 15

Load/Save menu (TR)

YRM-502 Load/Save menu

The screen of the Load/Save menu is divided between the command line and a list of all available commands.

The command line of this screen is reserved for the specific Load/Save commands.

If you use the SFG-01 module, the commands that require a disk are not displayed in the list.

To quit this screen, you need to press the ESC key.

Command Meaning
CL f CLOAD [filename] Load data from cassette tape
CS f CSAVE filename Save data on cassette tape
DD f DISK DELETE filename Kill data file on disk
DF DISK FILES LIst of files on disk
DL f DISK LOAD filename Load data from disk
DS f DISK SAVE filename Save data on disk
RL f RAM CARTRIDGE LOAD filename Load data from data memory cartridge (UDC-01)
RS f RAM CARTRIDGE SAVE filename Save data on data memory cartridge (UDC-01)

  • There is a bug in the initial release of the FM Voicing Program II shipped prior october 1986 (Rom Dump CRC 51F7DDD1). When you save a voice bank on disk ("VOG" file), it eliminate the last 32 bytes of the file, so this "short" file (3079 bytes instead of 3111) eliminates the data for operator #3 and operator #4 of the last voice #48. Yamaha released a corrected version of the FM Voicing Program II (Rom Dump CRC 5330FE21)

Key lists (F5)

YRM-502 Command key list (F5)
YRM-502 Edit key list (F5)
YRM-502 Common key list (F5)

The Key lists screen displays a list of the most important keys to be used with this software. Distinction is made according the mode that you are using ('general' command line, Edit mode, Load/Save menu).

The command line is not available on these screens. Press on ESC to go back to previous displayed screen.

Here's a more complete list that integrates all the modes of this software:

F1 Go to Edit Mode or switch between blocks and the command line in Edit mode (not available in Load/File menu)
F2 Decrease velocity
F3 Increase velocity
F4 Load current voice data to instrument 2 for the comparison keyboard
F5 Go to the Key list corresponding to the mode you are using
All cursors Select parameter in Edit mode
Left cursor Previous voice when you are on the main command line
Right cursor Next voice when you are on the main command line
BS Correction for Voice Name in Edit mode or command on command line
CODE/KANA/HANGUL Switch hardcopy density
CTRL + 1 Switch ON/OFF operator 1 in Edit mode
CTRL + 2 Switch ON/OFF operator 2 in Edit mode
CTRL + 3 Switch ON/OFF operator 3 in Edit mode
CTRL + 4 Switch ON/OFF operator 4 in Edit mode
CTRL + P Hardcopy of current screen
CTRL + R Replace the data of the currently edited voice by the data saved in the save buffer (in Edit mode)
CTRL + S Save the data of the currently edited voice in the save buffer (in Edit mode)
CTRL + STOP Stop loading/saving operation, hardcopy
CTRL + TAB Restore operator in its previous state (before copy operation with TAB) in Edit mode
CTRL + Z Switch the key click ON/OFF
DEL Increase value (+1) in Edit mode
ESC Back to previous screen when you are on a Key list screen, cancel not yet entered command
HOME Decrease value (-1) in Edit mode
INS + DEL Increase value (+10) in Edit mode
INS + HOME Decrease value (-10) in Edit mode
RETURN Enter new value (or name) for parameter in Edit mode, enter command on command line
SELECT followed by a key on music keyboard Change music keyboard split point
SPACE Insert space in Voice Name in Edit mode or in command on command line
TAB Copy the data of an operator to another operator in Edit mode