I want to use the downloaded music file on my device with the monaca app.

What do you want to do with the environment and music?Please write about and so on.
monaca must have an external plug-in available for implementation with the above features.

Also, you would like to use the music file, but
I can play it, but it's hard to say what to do directly with the music file.
(There is a high possibility of rejection due to the nature of the work.)

If an external plug-in is available,
Playback may be implemented using the plug-in here.

When it comes to music files... is it like maximum volume + microphone sound acquisition during playback?
Either way, I don't recommend handling music files directly because they smell dangerous.