Adding a line-in to Picasso CD? - Steve Pearce
Does anyone know of a way of adding a line input to the standard Picasso CD? I have a MP3 player I would love to play through the speakers but with a lack of cassette I have no easy way of interfacing. I was hoping to make it think I had a CD multi-changer (which I haven't) and fake it somehow.
Adding a line-in to Picasso CD? - Vagelis
I guess the Picasso CD is a model-specific unit, so unless it has a line-in jack, methinks you're out of luck :-|

Vagelis.
Adding a line-in to Picasso CD? - Altea Ego
Unlikely you can use the CD changer jack. Its umlikely to have an aux port. Your best bet is an in line rf modulator in the aerial lead.
Adding a line-in to Picasso CD? - Steve Pearce
I suspect it can be done, these people seem to be inventing adaptors to do just this:

www.connects2.co.uk/index.html

However they don't have one for Citroen yet.