Is it possible to assign a sound when plymouth is running ? If so how ?
Hi,
I don’t know about playing sounds during boot but you can try using this:
If you mean a normal login sound, there’s this:
Try this solution. I haven’t tried it, but it worked for them.
Specifically, create a file in /etc/init/boot-sound.conf containing:
# boot-sound - Play sound when booting
#
description "Boot sound"
start on filesystem or runlevel [2345]
# play the sound
exec /usr/bin/aplay /usr/share/sounds/boot-sound.wav
Then place your sound file at /usr/share/sounds/boot-sound.wav. You’ll need to be root to write to these areas.
Bare in mind the system is still booting, so results may vary on whether the system has initialised all audio devices.
To test:
sudo start boot-sound
Again, I haven’t tested this to be sure it works or if something different then aplay is needed.
It did not work for me 
I don’t think it is possible to actually play a sound while booting?. 
All I have found are threads for “Login sound” only!. 
Sorry, my findings doesn’t seem to work - I just had a bit of an experiment.
In theory, it could work, since the system executes a series of scripts to start the system. It’s just the matter of priorities and being able to create one properly and execute it after the sound system has been fully initialized.
in fact, you have how to "play music" in GRUB ... there are some scripts ready like the theme of stat wars, and many others ... having time put here
y que hay de systemmd por que no poner un script que se ejecute despues del demonio de la tarjeta de sonido...?