HTC 4350 (Vodafone VPA III compact) has a combined USB/Audio cable.
It is rumored to be an 11pin connector plug compatible with the mini USB.
There are some commercially available, see e.g. (sorry both links are in german):
http://www.amazon.de/HTC-Stereo-Converter-f%C3%BCr-Kopfh%C3%B6rer/dp/B000VI5Z0Q/ref=pd_sbs_ce_njs_title_2
or
http://www.amazon.de/Y-Adapter-3-fach-Mini-USB-Freisprecheranschluss-Converter/dp/B000UJZDLC/ref=pd_sbs_ce_njs_title_3
Does somebody have more info?
regards
Bernhard