NINEIGHT Composer

A browser-based FM synthesizer emulating the legendary Yamaha YM2608 (OPNA) sound chip, best known for its use in NEC PC-98 computers and classic Japanese arcade games. Currently in development.

What is OPNA?

The YM2608, also known as OPNA (OPN with ADPCM), is a sound chip manufactured by Yamaha in the late 1980s. It was the heart of the NEC PC-9801 series computers and became synonymous with the distinctive sound of Japanese PC gaming during that era.

Technical Specifications

• 6 FM channels using 4-operator synthesis
• 8 algorithms for operator routing
• 3 SSG/PSG channels (legacy sound)
• ADPCM channel for sampled audio
• Stereo output with per-channel panning

How FM Synthesis Works

FM (Frequency Modulation) synthesis creates sound by using one waveform (the modulator) to modulate the frequency of another waveform (the carrier). This technique produces rich, complex timbres from simple sine waves.

The 4-Operator System

• Operators 1–4: Each has its own envelope (ADSR), frequency multiplier, detune, and output level
• Algorithms 0–7: Define how operators modulate each other
• Feedback: Operator 1 can modulate itself for added harmonic content

Envelope Parameters (ADSR)

• AR (Attack Rate): How fast the sound reaches full volume
• DR (Decay Rate): How fast it drops to sustain level
• SL (Sustain Level): The held volume level
• RR (Release Rate): How fast sound fades after note release
• TL (Total Level): Overall operator volume

Additional Parameters

• MUL (Multiplier): Frequency ratio (0.5× to 15×)
• DT (Detune): Fine pitch adjustment for richness
• KS (Key Scaling): Higher notes decay faster
• AM (Amplitude Modulation): LFO tremolo effect
• SSG-EG: Special looping envelope modes

The Emulator

This synthesizer uses YMFM, an accurate cycle-accurate emulation core for Yamaha FM sound chips, compiled to WebAssembly for browser playback.

Features

• Real-time audio synthesis in the browser
• Accurate emulation of YM2608 behavior
• Low-latency playback via Web Audio API
• No plugins or downloads required

Controls

Keyboard

Piano keys are mapped to your computer keyboard:

Row	Keys	Notes
Bottom	Z X C V B N M	C D E F G A B
Middle	A S D F G H J	C D E F G A B (+1 oct)
Top	Q W E R T Y U	C D E F G A B (+2 oct)

Shortcuts

Key	Action
[ / -	Octave down
] / =	Octave up
Up / Down	Change preset
1	Toggle CRT effect
CTRL + D	Download patch as JSON
F1	Start/stop recording
Left / Right	Move Hibiki
Space	Toggle Hibiki pose

MIDI Support

Connect a MIDI controller and click Enable MIDI to play with external hardware. The synth supports:

• Note On / Off
• Velocity
• Octave sync
• Arpeggiator integration

Drag & Drop

Drop a .json patch file onto the synth to load custom instruments.

The Sound of an Era

The YM2608 defined the sound of countless classic games and software:

• Touhou Project series
• Ys series (Falcom)
• Dragon Slayer series
• Brandish
• Popful Mail
• Countless PC-98 visual novels and games

Its warm, distinctive FM tones combined with the SSG channels created a unique sonic palette that remains beloved by retro gaming enthusiasts and chiptune artists worldwide.

Development

NINEIGHT is still in development. I am working on an MML editor to compose melodies, which is where the “Composer” in the title comes from. It will allow importing FM, SSG, and ADPCM instruments in order to create songs.

Credits

• YMFM: Emulation core by Aaron Giles
• Phaser: Game framework

For more PC98 music

For more PC-98 music, check out my YouTube channel! I upload two calm PC-98 mixes every week. Subscribe if the music resonates with you!

https://www.youtube.com/channel/UCJzBq5knN3d5eG0_4QDEQpw

Also you can check:

https://delacannon.itch.io/necvgm