$D406/54278/SID+6:   Voice 1: Sustain / Release Cycle Control

   +----------+---------------------------------------------------+
   | Bits 7-4 |   Select Sustain Cycle Duration: 0-15             |
   | Bits 3-0 |   Select Release Cycle Duration: 0-15             |
   +----------+---------------------------------------------------+

   This register is write-only!

   See also: ADR-Rates