it's just using a tremolo combined with fast refresh rate on the square channels. it is used a bit on the noise channel, but it sounds very thin in the vgm compared with the snm file, so i didn't use it much.
post #128289 ::
2020.10.11 10:46am :: edit 2020.10.11 10:46am kleeder liēkd this
the z80 will still be clocked at ~4MHz, it's just that the music engine isn't waiting for a vblank interrupt to start it's routine every ~60Hz. It's operating at a higher refresh rate.