Moonsound

Lore & Background

Moonsound was created and designed by electronic engineer Henrik Gilvad on a semi-hobby basis. It was unveiled at the Tilburg Computer Fair in 1995, two years after Microsoft abandoned the MSX platform in 1993 in favor of IBM PC compatible platforms. At least two generations were made: an early version with a small PCB without a protective shell, and a later version with a larger PCB that fit into a standard MSX cartridge.

The sound card is based on the Yamaha YMF278 (OPL4) chip, capable of 18 channels of FM synthesis and 24 channels of 12- and 16-bit sample-based synthesis. Its FM registers are compatible with OPL, OPL2, OPLL, and OPL3 chips, allowing some older software to use its FM portion. The card was equipped with one 128 KB SRAM chip from the factory for compressed user samples; later versions (1.1 and 1.2) had two sockets for up to 1 MB SRAM, and some modders have stacked additional chips to reach 2 MB. The 2 MB ROM contained 330 mono samples, mostly at 22.05 kHz at 12 bits, with some drums at 44.1 kHz.

The Moonsound's audio power supply is isolated from its digital supply to reduce noise. It does not mix with the internal MSX sound but uses a separate stereo audio output. Sound effects like chorus, delay, and reverb were omitted due to cost, size, and usability reasons; the Yamaha effect chip required its own memory and offered basic routing, with all channels sharing the same effect setting. Programmers created pseudo effects by overdubbing or using dedicated channels for delayed notes with stereo panning.

Reader's Guide

Moonsound's significance lies in its role as a high-end sound card for the MSX platform after Microsoft's withdrawal from the market. By combining FM synthesis and sample-based synthesis in a single cartridge, it offered capabilities that were unusual for its time, particularly the 2 MB instrument ROM containing multisampled instruments. Its compatibility with earlier OPL-family chips allowed some existing software to use its FM portion, broadening its utility.

The card was supported by a dedicated software ecosystem, most notably Moonblaster, a time-step sequencer designed by Remco Schrijvers and later developed by Marcel Delorme. Moonblaster came in separate FM and sample-based versions. Other software included MOD file players, MIDI file players, and a Music Macro Language compiler. Henrik Gilvad also developed tools to rip sound loops from audio CDs via SCSI or ATA-IDE interfaces.

Moonsound has been emulated in MSX emulators such as blueMSX and openMSX, ensuring its continued accessibility. While its omission of hardware effects limited its complexity, the card remains a notable example of late-era MSX hardware development, driven by hobbyist and small-company efforts.

Did You Know?

• Moonsound was named after its accompanying Moonblaster software.
• Some modders have stacked additional SRAM chips to achieve up to 2 MB of user sample memory.