Hi Alan!
What I have done so far is use Ardour with JACK
running at 48KHz to pull
off the music. Then, I exported it to a WAV and used AlsaPlayer to
playback the audio at approx 25% normal speed.
I think the optimal solution concerning quality was to record at 192 kHz
and process the resulting file at 48 kHz...
Ciao,
HippiE