I've got an old iPod (pre-classic) and sometimes it manages to connect, other times not. It's annoying enough that I'm just going to dump all my songs on an SD card and stick it in the center console.
Follow what has been posted on here about the SD card.
I had a old micro 16g sdcard and adapter that I used in an old phone. It was real flakey in the yuk. As in it took a long time to read and sort thru songs, it would start playing a song and then hang, sometimes not show up when the media button was pushed with "No Media Found", voice control seemed like it wasn't woking, etc.
Got mad, ordered a 32g sdcard only. Made sure it was formated to Fat32 and dropped songs and videos on to it.
Works great now, yukon read the entire card in less than 15 seconds with it being 3/4ths full. Videos run smooth and no delay in Browsing the card with the display.
Voice control has no problem with it. Tell it what song you want to hear, once that song is done, it will play the next song in alphabetical order, no matter what band it is in your library. If you chose a band it will play every song you have on the card of that group.
Works really well for road trips, I hope. We'll see in a couple of weeks.