Play MIDI song such as LAVENDER.MID or PLANETAL.MID.
Mute channel 1.
Set speed to anything other than 1.00.
Seek forward to mid-song.
Then
Artwork disappears.
Speed appears reset to 1.00.
Channel 1 appears to become unmuted.
(Possibly exposed by 326322d0ac1b4eb6156febecfc183e5b144d8f1c because mute mask appears reset when instruments change.)
Given
Then
Given
Then