- Yamaha OPL4 sound processor (YMF-278B-F)
- 100% OPL1/OPL2/OPL3 compatible (note: the MSX-Audio is also OPL1 compatible, so MSX-Audio software that doesn't use the MSX-Audio ADPCM part can be used on the OPL4)
- OPL4 is an independent CPU with it's own memory so even a slow 3,58 MHz MSX computer is able to replay high quality samples with minimum of CPU power
- Wave table part: 24 PCM channels (stereo: adjustable in 16 steps for each channel; replay frequency up to 44.1kHz)
- Replay of 8-bit, 12-bit or 16-bit data
- support for 2MB of SRAM for own samples
- FM synthesizer
- 18 2-operator FM channels
- 15 2-operator FM channels + 5 FM drums
- 6 4-operator FM channels + 6 2-operator FM channels
- 6 4-operator FM channels + 3 2-operator FM channels + 5 FM drums
- 2MB wave table ROM (Yamaha YRW-801) with (approx.) 330 samples, mostly 22kHz 12-bit
- Compatibility with the General MIDI standard (128 melody sounds and 47 percussion sounds)
Here's an example which shows how the Yamaha OPL4 can perform.
MoonSound is a high-quality 16-bit wave table and FM soundcard for MSX computers, based on the Yamaha OPL4 standard. Different versions of the MoonSound were made. Also the output connector in this first series is on a different place; on top of the cartridge. In version 2 the output connector is on the right side of the cartridge.
MoonSound version 1 has 128kB SRAM (1 socket) and version 2 a socket for a second SRAM IC. This can either be a 128kB SRAM chip (Part number: SONY CXK581000AP, Memory Capacity: 1M-bit, Function: (128k × 8-bit) LL, Access: 70 ns, Pins: 32, Package: DIP) or a 512kB SRAM chip (Part number: HITACHI HM628512LP-7, Memory Capacity: 4M-bit, Access: 70 ns, Pins: 32, Package: DIP).
The MoonSound comes with a cable (mini jack to 2 × cinch; stereo) to connect it to an amplifier. Also a black & white manual and the Moonblaster software is included.
Other compatible clones of the MoonSound are the Korean DalSoRi (which means MoonSound in Korean), the Brazilian OPL4 Shockwave and the Argentinian Wozblaster.
All clones can hold 1 MB of sample-RAM and have the 2 MB Yamaha YRW801-M General MIDI ROM on board. However, technically the OPL4 can address 4 MB SRAM if no 2 MB Yamaha ROM is present.
The DalSoRi is the smallest version which is Konami case-sized. The MoonSound fits the medium size NMS-1250 modem case. The Wozblaster doesn't come with case. The OPL4 Shockwave is the largest version. Unlike Moonsound and Wozblaster, that uses the Yamaha YAC513 as DAC, the DalSoRi uses the Philips UDA1330A instead and the OPL4 Shockwave the Sanyo LC78815M. According to their manufacturers they provide better sound quality and low noise.
MSX-Audio BIOS support
The FM part of the OPL4 part began being supported by the MSX-Audio BIOS since v1.3, including stereo sound. Unfortunately, none of the currently existing OPL4 cartridges has a built-in circuitry capable of receiving MSX-Audio BIOS updates.