Y8950 MSX-AUDIO Test register $01 (write only) Bit Description 7 Reset LFOs - seems to force the LFOs to their initial values (eg. maximum amplitude, zero phase deviation) 6 something to do with ADPCM - bit 0 of the status register is affected by setting this bit (PCM BSY) 5 No effect? - Waveform select enable in YM3812 OPL2 so seems reasonable that this bit wouldn't have been used in OPL 4 No effect? 3 Faster LFOs - increases the frequencies of the LFOs and (maybe) the timers (cf. YM2151 test register) 2 Reset phase generators - No phase generator output, but envelope generators still work (can hear a transient when they are gated) 1 No effect? 0 Reset envelopes - Envelope generator outputs forced to maximum, so all enabled voices sound at maximum