Uploaded August 2016 | Updated September 2026, 1 week ago
Who says the American NES can't do expansion sound?
The Japanese version of Castlevania III, a.k.a. Akumajou Densetsu (悪魔城伝説) is well known for its richly orchestrated soundtrack that included extra sound hardware inside the cartridge known as the Konami VRC6. Unfortunately, outside of Japan, the NES did not have support for this kind of expansion audio, and the soundtrack on other versions had to be scaled back significantly.
This little demonstration takes on the problem of no expansion audio hardware, by using the CPU of the NES to synthesize two extra square wave channels to make up for what's missing. I had to make some changes to the arrangement to make it fit, but at long last you can hear something close to the Japanese Castlevania III soundtrack coming out of an unmodified North American NES!
ROM download: rainwarrior.ca/projects/nes/ad_sound_demo.nes
NSF music file: rainwarrior.ca/projects/nes/ad_sound_demo.nsf
Engine used, with source code:
rainwarrior.ca/projects/nes/dmmc_beta.zip
Recorded from a real North American model NES. Download the ROM to try it yourself. No hardware modifications are necessary.
Sadly, this technique wouldn't really work in a game setting, since the CPU is being used heavily there is really not enough time left in a frame to run a game while playing this music. This is merely a proof of concept.
rainwarrior.ca
Who says the American NES can't do expansion sound?
The Japanese version of Castlevania III, a.k.a. Akumajou Densetsu (悪魔城伝説) is well known for its richly orchestrated soundtrack that included extra sound hardware inside the cartridge known as the Konami VRC6. Unfortunately, outside of Japan, the NES did not have support for this kind of expansion audio, and the soundtrack on other versions had to be scaled back significantly.
This little demonstration takes on the problem of no expansion audio hardware, by using the CPU of the NES to synthesize two extra square wave channels to make up for what's missing. I had to make some changes to the arrangement to make it fit, but at long last you can hear something close to the Japanese Castlevania III soundtrack coming out of an unmodified North American NES!
ROM download: rainwarrior.ca/projects/nes/ad_sound_demo.nes
NSF music file: rainwarrior.ca/projects/nes/ad_sound_demo.nsf
Engine used, with source code:
rainwarrior.ca/projects/nes/dmmc_beta.zip
Recorded from a real North American model NES. Download the ROM to try it yourself. No hardware modifications are necessary.
Sadly, this technique wouldn't really work in a game setting, since the CPU is being used heavily there is really not enough time left in a frame to run a game while playing this music. This is merely a proof of concept.
rainwarrior.ca
