About the SID native waves:

$11 = triangle wave
$21 = sawtooth waveform
$41 = pulse waveform (pulse sweep also needed)
$81 = noise wave

$11 = "Attack" cycle starts
$10 = "Release" cycle starts

Waveform bits, value construction (for $d404, $d40b, $d412):

%00000000
         ^- gate bit (+$01)
        ^- sync bit (+$02)
       ^- ring modulation bit (+$04)
      ^- test bit (+$08)
     ^- triangle waveform (+$10)
    ^- sawtooth waveform (+$20)
   ^- Pulse waveform (+$40)
  ^- Noise waveform (+$80)

About the bit combinations:

$00       = silence, gate off (release cycle)
$01       = silence, gate on (attack/decay/sustain): volume present

$02...$07 = not used
$08       = Test bit (kind of "hard restart"): reset tone + Release set
$09       = Also some kind of "hard restart": reset tone + ADS cycle set
$0a..$0f  = not used (only gate on/off)

$11,$10   = triangle waveform (attack,release). NATIVE WAVEFORM

$13,$12   = sync triangle wave with previous channel.
           If set to channel #2:
           Channel 2 wave+freq will be combined with channel 1.
           (waveform+frequency affects the result on both channels)
           The resulting wave will be played in channel 2. Channel 1
           plays normally.
           The sync bit "set" will combine:
           (in channel 1): channel 1 combined with channel 3
           (in channel 2): channel 2 combined with channel 1
           (in channel 3): channel 3 combined with channel 2
$15,$14 = ringmod triangle wave with previous channel, similiar to
           sync bit. If set to channel 2:
           channel 1 frequency and channel 2 frequency will affect
           the result, not the wave.
$17,$16 = sync AND ringmod effect is affecting this waveform.
           (see values $12..$15)
$18...$1f = test bit set. Kills the sound, reset tone oscillator.

$21,$20 = sawtooth waveform (attack, release). NATIVE WAVEFORM

$23,$22 = sync a sawtooth wave, with previous channel. (see $12..$13)
$24...$27 = same as $20...$23. (no ringmod possible with this wave!)
$28...$2f = test bit set. Kills the sound, reset tone oscillator.
$30...$3f = triangle AND sawtooth combined wave. Plays different on old
             SID's. See $10..$1f and $20..$2f for details.
             Results like as $10...$1f waveform bits, not only
             like $20..$2f. NOT AN USUAL WAVE.
             Both ringmod and sync effects possible.

$40...$4f = pulse waveform. NATIVE WAVEFORM.
             You MUST set the pulse width when using this waveform.
             Results like $20..$2f.

$50...$5f = pulse AND triangle combined waveform. Effects like $10..$1f.
             sync and ringmod effects possible. Pulse width affects this
             waveform (the tone dies completely with widths of
             $800..$fff)
$60...$6f = pulse AND sawtooth combined waveform. Effects like $20..$2f.
             No ringmod effect possible. NOT AN USUAL WAVE. Silent with 

             a 6581 SID.
$70...$7f = pulse AND sawtooth AND triangle waveform combined.
             Effects like both $10..$1f and $20..$2f. pulse+ringmod are
             possible. NOT AN USUAL WAVE. Very silent with 6581.

$81,$80 =   noise waveform. NATIVE WAVEFORM.

$82-$83,$86-$87 = a slight SYNC effect.
$88-$8f =   reset noise
$90-$bf =   not used (do not use: the noise dies)
$c0..$cf =  rare extras(*)
$d0..$ef =  not used (do not use: the noise dies)
$f0..$f7 =  (*) rare extas: resets the internal pseudo random
             generator...
$f8..$ff =  : resets the internal pseudo random generator,
             so the noise waveform play different, on some sids the
             selected noise sounds more "metallic" depending on the
             value and running SID cycles and other status.
             Usage: first $f9, then $81

-- 
Agemixer of Skalaria