Yamaha SFG-05
This page was last modified 10:08, 6 June 2021 by Gdx. Based on work by Mars2000you and Rderooy and others.
Yamaha SFG-05.jpg



SFG-05 Polyphonic mode (F2)

The SFG-05 FM Sound Synthesizer Unit II is a FM music expansion with MIDI interfaces. The FM tone generator used is called OPP (YM2164). The cartridge contains also a stereo DAC (YM3012) and a MKS (YM2148). It is the second version of the SFG sound modules developed by Yamaha for their CX series.

The main diffence compared to the SFG-01 is the ROM that doubles in size. This new ROM of 32KB (MBIOS 2.0) has support for MIDI input, so it allows the internal FM synth to be played by any external MIDI keyboard. Other improvements are included: disk and printer support, loading of user voices, recording of auto bass chords.

It was released by Yamaha in 1984. Official launch price: ¥29,800. It was also sold by the educational NHK Gakuen school corporation.


  • OPP = FM Operator Type-P
  • DAC = Digital to Analog Converter
  • MKS = MIDI Interface & Key Scanner
  • MBIOS = Music BIOS (same name as the BIOS from MSX-AUDIO but totally different)


From BASIC, the music firmware can be launched with CALL MUSIC or _MUSIC. If the module is used on a machine with MSX-MUSIC in a lower slot, you have to make the distinction between both extensions: to start the SFG firmware in this case, enter CALL MUSIC plus any additional letter or number (eg _MUSICA)

Note that on the MSX2+ Sanyo and Sony machines with built-in MSX-MUSIC, this ROM is in slot 3-3. The SFG-05 module can only be added into a lower numbered slot, therefore CALL MUSIC will always run the SFG firmware when this module is present (even with additional letter or number).

The firmware starts in POLY(phonic) mode. By default, the EORGAN2 (electric organ 2) voice is selected for both instruments 1 and 2 and the music keyboard is split around the C3 center key: keys to the right play instrument 1 in split mode, the other keys play instrument 2 in this mode.


SFG-05 Monophonic mode (F1)

The SFG-05 firmware is divided into 4 screens, the bottom of each screen includes a visualisation of the music keyboard and the indication of some important keys.

The 4 firmware screens can be called using the functions keys F1 to F4.

Use the up and down cursors to see all the functions, the left and right cursors to change the settings.

SOLO (F1) and POLY (F2) screens

Several functions are common to SOLO (or monophonic) mode and POLY(phonic) mode, but many functions are exclusively available for a specific mode.

Function SOLO POLY
VOICE #1 X X 46 presets + 2 reserved voices + 48 user voices (see Yamaha FM Sound Synthesizer Unit)
VOICE #2 X X Needs to be activated in MIDI section for the polyphonic SINGLE mode
VOICE #3 - X Needs to be activated in MIDI section
VOICE #4 - X Needs to be activated in MIDI section
VOLUME X - Volume (0-13) for the sound played on the music keyboard in SOLO mode
VOLUME #1 - #4 - X Volume (0-13) for voice #1- #4 in one of the polyphonic modes
BALANCE X - Balance of the 2 voices in SOLO (monophonic) mode
PLAY MODE - X Three polyphonic modes: SINGLE - SPLIT - DUAL
SUSTAIN X X Sustain effect ON/OFF
DETUNE X X Detune effect only for DUAL and SOLO modes (0-13)
OCTAVE #1 - #2 X X Move instrument 1 or 2 up down one octave
TRIGGER X - Trigger effect with 2 modes: MULTI - SINGLE
PORTAMENTO X - Portamento effect ON/OFF
PORTAMENTO MODE X - 2 portamendo modes: FINGER(ed) - FULL (time)
PORTAMENTO RATE X - Faster of slower glide between notes with portamento effect
SPEED X X Slower or faster speed of the Low Frequency Oscillator (frequency)
TREMOLO X X Periodicity of the changes in volume (0-13)
VIBRATO X X Periodicity of the changes in pitch (0-13)
RHYTHM BASS X - 2 bass voices: R1.BASS - R2.BASS
RHYTHM CHORD X - 4 chord voices: RM.BRAS(s) - RM.FLUT(e) - RM.GUIT(ar) - RM.HORN
RHYTHM VOLUME X - Volume of the rhythm section (0-13)
RHYTHM CHORD MK X - Part of the music keyboard reserved for Auto Bass Chord ON/OFF
RHYTHM START MODE X - When using F5 to start the rhythm, normal mode or synchronized mode (pressing of a key on the music keyboard)
TEMPO X X Slower or faster speed of rhythm (important for playback or recording)
TRANSPOSE X - Transpose up down in half-steps, to a maximum of 7 steps
TUNING X - Adjust the tuning less than a half-step, to a maximum of 1/2 step up or down
MIDI CHANNEL X - MIDI Reception channel (1-16) in SOLO (monophonic) mode
MIDI CHANNEL #1 - #4 - X MIDI Reception channel #1 - # 4 (1-16) in one of the polyphonic modes
CLOCK X X Clock used for synchronisation with MIDI device: internal or MIDI device

VOICE screen (F3)

SFG-05 Voice menu (F3)

By default, this screen displays the system voices (see Yamaha FM Sound Synthesizer Unit) and highlights the current selected voices: in white for instrument 1, in yellow for instrument 2.

To change the selections, use the cursor keys, then press SPACE or RETURN when the arrow points to the wished instrument. SWitching instruments 1 and 2 can be done by pressing SELECT.

To switch between the system voices and the user voices, press twice quickly the SELECT key. This can also be done outside the VOICE screen.

FILE screen (F4)

SFG-05 Load/Save menu (F4)

This screen allows to load/save data from/to cassette, cartridge or disk. The name of the file can be entered on the third line of this screen.

The cartridge in question is the UDC-01 Data Memory Cartridge, which is internally identical to the Sony HBI-55 Data Cartridge. This device can be used by the Yamaha YRM-102 FM Voicing Program and YRM-502 FM Voicing Program II cartridges (the YRM-502 was also build in the CX5MII and CX7M-128 computers).

Here are the different possibilities:

OPERATION Cassette Cartridge Disk
Load voice data (.VOG file on disk) X X X
Load event data (.EVG file on disk) X - X
Save event data (.EVG file on disk) X - X
Kill a file (only .EVG file) - - X
Files - - X

Number of notes per instrument with MIDI

8 notes can be produced simultaneously. Without activating instruments 3 or 4 for MIDI in POLYphonic mode (and instrument 2 in SINGLE mode), the number of notes you can play is not different if you use a music keyboard or a MIDI keyboard: 8 notes in SINGLE mode as only one instrument is used, 4 notes for instruments 1 and 2 in SPLIT and DUAL modes.

If you activate the 'extra' instruments to receive MIDI, there are more different situations in SINGLE and SPLIT modes:

PLAY MODE Pattern Instrument 1 Instrument 2 Instrument 3 Instrument 4
B 6 notes 2 notes OFF OFF
C 6 notes OFF 2 notes OFF
D 6 notes OFF OFF 2 notes
E 4 notes 2 notes 2 notes OFF
F 4 notes 2 notes OFF 2 notes
G 4 notes OFF 2 notes 2 notes
H 2 notes 2 notes 2 notes 2 notes
SPLIT I 4 notes 4 notes OFF OFF
J 3 notes 3 notes 2 notes OFF
K 3 notes 3 notes OFF 2 notes
L 2 notes 2 notes 2 notes 2 notes

Useful keys

F1 Select SOLO (monophonic) mode
F2 Select POLY(phonic) mode
F3 Select VOICE mode
F4 Select FILE mode
F5 Start/Stop Auto Rhythm in SOLO mode
Left and right cursors Change settings ; move arrow in VOICE mode, vertical arrow in FILE mode
Up and down cursors Select function; move arrow in VOICE mode
BS Erase one character to the left of vertical arrow for FILE NAME in FILE mode
CTRL + STOP Stop printing when making a hardcopy of the screen
DEL followed by INS Start music keyboard or auto bass chord recording in RAM
ESC Back to YRM-102 or YRM-502 FM Voicing Program
GRAPH Switch display or not of the notes on the on-screen music keyboard when they are played on the real music keyboard
HOME Select printer type and hardcopy density (F4 window on the bottom of the screen)
HOME x 2 Start hardcopy of current screen
INS Start music keyboard or auto bass chord playback from RAM
RETURN Select voice in VOICE mode, execute/confirm selected operation in FILE mode
SELECT Switch instruments 1 and 2 in VOICE mode
SELECT x 2 Switch system voices and user voices in VOICE mode
SELECT followed by a key on music keyboard Change music keyboard split point in POLY mode
SHIFT + left or right cursor Fast change settings
SPACE Select voice in VOICE mode
STOP Stop printing selection, split point procedure, music keyboard or auto bass chord recording or playback in/from RAM
TAB Hidden feature, which displays 'M5.01.011' in the F4 window on the bottom of the screen