I tried using an SD card loaded with ripped music for the first time the other night.
It was a 32GB card, with about 24GB of music (MP3 and AAC formats). Probably about 3500 songs.
Upon inserting the card, the dash display seems to be scanning through the songs, in alphabetical order (by artist name). The songs are not available to be listened to during this process.
Here's the problem(s) -- first of all, it will take hours of uninterrupted driving for for the stereo to scan all of the songs.
Second, if I change the audio input during the scanning process (listen to music via iPhone for example), the scanning process stops.
If I eject the card, and reinsert it, the scanning starts from the beginning.
If I let the scanning continue, it eventually stops when it reaches artists in the "D" range, and only gives me access to those songs.
I've got a 2012 Passat, with no navigation system, and my stereo has two knobs, not three. The card is SDHC, formatted for Windows. The music files were copied directly to the preexisting "My Music" folder on the card from iTunes.
Also, unrelated to above issue, when using iPhone for music, some songs seem to be missing certain audio tracks -- for example, backing vocals on some songs, guitar on others?