$D404/54276/SID+4:   Voice 1: Control Register

   +-------+------------------------------------------------------+
   | Bit 7 |   Select Random Noise Waveform, 1 = On               |
   | Bit 6 |   Select Pulse Waveform, 1 = On                      |
   | Bit 5 |   Select Sawtooth Waveform, 1 = On                   |
   | Bit 4 |   Select Triangle Waveform, 1 = On                   |
   | Bit 3 |   Test Bit: 1 = Disable Oscillator                   |
   | Bit 2 |   Ring Modulate Osc. 1 with Osc. 3 Output, 1 = On    |
   | Bit 1 |   Synchronize Osc. 1 with Osc. 3 Frequency, 1 = On   |
   | Bit 0 |   Gate Bit: 1 = Start Att/Dec/Sus, 0 = Start Release |
   +-------+------------------------------------------------------+

   This register is write-only!