diff --git a/audio-v2.md b/audio-v2.md
index 0d49016..057e6b0 100644
--- a/audio-v2.md
+++ b/audio-v2.md
@@ -62,6 +62,8 @@ specified in 10ms increments (e.g. `0x03` is 30ms). The S port for
 So with a value of `0xff` the note would hold as long as possible, and
 with `0x00` the release would occur just after the decay ends.
 
+(If the duration is short parts of the envelope may be truncated.)
+
 Since each component has its own port, it's also much easier to adjust
 one without having to fiddle with bit masks, shifting, etc.
 
@@ -73,7 +75,7 @@ one without having to fiddle with bit masks, shifting, etc.
     0x32  2 bytes  duration  duration to play sound in fractional seconds (1ms resolution)
     0x34  1 byte   attack    envelope: attack duration (vol 0-100%, 10ms resolution)
     0x35  1 byte   decay     envelope: decay duration (vol 100-50%, 10ms resolution)
-    0x36  1 byte   sustain   envelope: sustain duration (vol 50%, 10ms resolution)
+    0x36  1 byte   sustain   envelope: sustain fraction (vol 50%, x/255 of free time)
     0x37  1 byte   release   envelope: release duration (vol 50-0%, 10ms resolution)
     0x38  2 bytes  addr      address to read waveform data from
     0x3a  2 bytes  length    length of waveform data to read (in bytes)