[P-ToK72]

I use a couple of USB connected portable hard drives (can remember the size off the top of my head) with my collection of music that is in the format of standard MP3 files (CDs ripped through iTunes).

With my previous BMW 3 series I reached a maximum number which could be read from one source so had to split it down onto a second hard drive but I am nit sure if this has changed with the idrive 7.

I do have a pdf copy of the audio manual which I can send you if you dm me your email address. I haven't studied the routes of other formats but the book says MP3, MP4, M4A, M4B, AAC and WMA.