I'm wondering what could be causing the following:

When I listen to mpd audio from GNU Emacs, the volume drops significantly after exactly one minute of play.

It doesn't happen when playing audio from the N900's media player.

If while playing from mpd and the audio drops, I switch to the media player which is paused, playing something else, and just click on play and pause immediately, the sound from mpd keeps playing and the volume picks up again.

After another minute it drops again and so on.

Anybody have any thoughts on what could be causing this?

What's mpd?
Can you avoid short naming convention, it helps everyone to understand.

Music Player Daemon, man, in GNU/Linux generally referred to as mpd...
http://mpd.wikia.com/

It's a very memory efficient server you can use to play music with minimum CPU usage, very good exactly for devices of this type, much less memory hungry than mplayer for example (GNU/Linux Media Player, called mplayer ).

Anyhow, the problem with the audio dropping is a bugger though. No thoughts so far on my side, think it might be pulseaudio related, am trying to figure out how to reload it or something, but it seems you can't access it as user on the N900, and neither as root... WTF?