I've been using GrapheneOS for a while now and it seems to me that listening to locally stored music drains my battery more than I expect. In an other closed thread, the Devs claimed the following:
Use a more efficient music playing app and codec which doesn't require using as much power. Avoid it having to decode something with a software codec and resample it. If you do something demanding that's not hardware accelerated, it's going to drain more power. Playing high sample rate FLAC is going to drain more power. It is not an OS or hardware issue draining power on your device, it's what you're doing that's draining power.
Since there are a whole lot of local-music players, me and others of that thread asked ourselves, which one might be "the best" in terms of battery efficiency. I don't know a whole lot about audio. Maybe someone could share their expertise or just by telling us, which application you are using, your helping those people a lot, who need a proper recommendation (including myself).
I can tell you that I started using VLC because of the options you have available f.e. I have hardware acceleration on "full". All the locally-stored music that I listen to have the same parameters:
Bitrate: 192 KB/s
Codec: MPEG Audio layer 1/2
2 channels
Sample rate: 44100 Hz
Sharing your expertise or information helps us a lot.
Thanks in advance.