If you're on GBPVR, you can edit the tuning file to record another audio program. I had to do that for PBS here as the AC3 stream was audio captioned for the visually impaired. I don't remember exactly where this is, but I think if you look in the tuning cache you can see all the audio and video streams for a channel. I had to change the ID of the audio stream I wanted to record. Sorry for the vague answer. If you look around in there a bit, I think you can figure it out.
HTPC: E7500, HD5450, HDHR Prime/Avermedia Duet A188, NPVR 3.3.8, Win7 Pro
Test: Asrock 890GM Pro 3, Athlon X2 255 , internal HD4290, ATI Theater 650Pro, NPVR 3.3.8, Win7 Home Premium
Backup: Athlon 3200, Nvidia 7600GT, NPVR 2.5.5, Win7 Home Premium