| 1111 || 0Fh || <code>/_________</code> || volume remains quiet
|}
==== Bit 3 (Continue) ====
We can observe that there are only 8 resulting shapes even though they are selected by using a 4-bit value. The continue bit does not exist internally.
In other words, we have:
shape = 1 if (ves >> 2 == 0) else 7 if (ves >> 2 == 1) else ves & 7
==== Bit 2 (Attack) ====
This bit is only responsible for the starting point of the envelope and the direction.
On other words, we have:
volume = 0 if attack else 15 # Start at 0 for attack, 15 for decay
direction = 1 if attack else -1 # Upward for attack, downward for decay
When using the volume envelope generator, the volume is always increased from 00h to 0Fh (or vice versa), it is not possible to specify a starting/ending point (like from 00h to 07h).