I can't get it reproduced, but......
I think I've found a bug/something strange in ARIA+GPO.
Very short notes,
CC#21 set to a low value.
When that CC#21 is at almost minimum level (value 5-10) AND
when the velocities are rather high AND
when the note duration still is very, very short [notated]
THEN I noticed some "wood hitting sound" after the played note (not every note) as if the player knocks on the wood of the instrument.
Making the note duration a bit longer, it disappears. There must be some mathematical relation between the duration of the note, sample length, and sample length set by CC#21. Don't know which....
By the way it also disappears (most of them) when I set the ARIA controls to some different value, like pre-cached from 96 to 64, DYN MAX from 512 to 256, inst.poli from 128 to 64.
Raymond - who never knocks on wood