Personally, I think encoding music to 64 bps, much less mono, is a waste of time.
In doing so, you will miss out on a lot of the intricate bits of the music.
64 bps mono is fine for speech, or non-music radio, as there is a small range of tones in speech, but not for music.
You just loose too much of the sound quality.
Music has multi levels of sound, and tones, that need to have a wider range to capture all the detail.
It's like listening to the same song on an AM station, compared to an FM station.
AM sounds like they're singing in a bucket.
What are you using to encode your music?
Have you tried encoding the same song at 64 bps mono, and 128 bps stereo, then listening to the difference?
If not, try it.
If you have a half decent system, you should notice definite difference between the two, in sound quality.
I suggest, at a minimum
, 128 bps stereo.
That's roughly equivelant to CD quality.
But, all of this is irrelevant.
It depends on what you