c64 basic prggies [query]

For a start you can mess around with the SID registers using POKEs.  As you know SID has 3 channels, each is mapped to 7 registers in sequence starting at 54272.  The registers after that control the global filter and volume.

For example try this to play some noise on channel 1.

10 POKE 54296,15
20 POKE 54277,0
30 POKE 54278,255
40 POKE 54276,129
50 POKE 54273,40

Explanation:

10 Set volume register (54296) to 15 (maximum)
20 Set Attack/Decay on channel 1 to 0 (no attack or decay)
30 Set Sustain/Release on channel 1 to 255 (full sustain and release)
40 Set Waveform on channel 1 to Noise (128) with Gate on so it doesn't fade out (+1 = 129)
50 Set raw pitch on channel 1 to 40.

Quick run down for channel 1:

54272 = Pitch low-bits (0-255)  (think of this as fine tune of the note)
54273 = Pitch high-bits (0-255)  (think of this as raw pitch of the note)
54274 = Pulse width modulation low-bits (0-255)
54275 = Pulse width modulation high-bits (0-15)  8 = Pure pulse wave
54276 = Waveform (17 = Triangle , 33 = Saw, 65 = Pulse, 129 = Noise)
54277 = Attack/Decay
54278 = Sustain/Release

Add 7 to the channel registers to play with channel 2 (eg: POKE 54276+7,129 to set waveform there) and 14 to play with channel 3 (eg: POKE 54273+14,40 to set the pitch on channel 3)

To activate the 'release' of a sound subtract 1 from the waveforms I listed above.  For example POKE54276,32 to turn the gate off on a saw wave on channel 1.

Best idea is to try out the programs in The Programmers Reference .  You want Chapter 4 which is all sound programs, including how the filters work.  Chapter 7 (the Appendix) has the pitch table for notes.