Yes, there are 128 MIDI note values, but 256 BBC SOUND quarter-note values which gives 64 note values, so a direct mapping has gaps at each end. Though as there are 2^7 MIDI note values and 2^10 SN7648 frequency values you'd think they would all fit, but being a linear to logrythmic mapping it doesn't come out like that!You have spotted a bug in the tables. The 2 tables do represent the 2 bytes for the SN76489 indexed by the midi note number, but as the chip cant go low enough to play the bass notes required I put some dummy values in, the pairs should be &8F and &3F which should be the lowest note possible.
It works easily mapping 64 SOUND note values to 128 MIDI note values though.
Statistics: Posted by jgharston — Tue Jan 27, 2026 11:48 pm