Thanks for your feedback.
I am using Ubuntu 21.10 and I am using MAME binaries compiled on this system. "sound" is set to "auto" in mame.ini.
All tracks are working well (from UI or command line) except track 3 and 16. The obvious difference between them is that track 3 and 16 use M6295 whereas the other use YM2612 (with regards blinking red spot)
Even if no sound is emitted, I can see the red spot blinking in front of M6295.
In PulseAudio Volume Control I can see a tiny, but constant, output while the spot is blinking, then it came back to plain 0 output when track finishes.
I checked in UI's slider control that all 4 M6295 channels volume is set to 1.0
Trying to find another game with YM2612 and M6295, I discovered that this game is actually declared with core YM3438 and not YM2612
<description>Hebereke no Popoon (Arcade)</description>
<publisher>Sunsoft / Atlus</publisher>
<info name="cores" value="YM3438, OKIM6295"/>
This seems to be related to a warning message at the command line:
mame vgmplay -quik heberpop:016 -window
Warning: file requests an unsupported YM3438
To explore a bit more, I tried to replace YM3438 with YM2612. This fixes the warning message, but still no sound.
Any idea ?