By “loud between the tracks”, he means mechanical noise from the drive spinning up to high speed and clicking while seeking the track. It will read the track at high speed, then spin down until time for the next track, and repeat the cycle for each track.
It is related to the problem of the CD drive spinning at high speed, which has not been fixed:
https://community.volumio.com/t/volumio-running-cd-drive-at-noisy-high-speed/54246/
The drive needs to read data at a low speed (no more than about 4x) for gapless to work. Otherwise the drive will spin down if it waits too long for the next data request.
@volumio, I’d like to ask what CD drives have been tested, and can you suggest a model that will stay spinning at a low speed.