An interesting music selection. Won't bore you with legal concerns and just give my oppinion about the music. The song lengths are mostly balanced, so you will hear different songs per race (2-3min is perfect i think). That is good. Some racing tunes are about 5 minutes, the showcase even 7 minutes - too long. Cut the showcase music to a nice loop, it will save filesize as well - in the end, you won't look so often and so long at a showcase.
Btw, what are the song-titles of the folk songs entitled "Show Ep4 1", "Show Ep34" and "Show Ep12" (GAME2, GAME8 & GAME16)? Are they from a TV show?
Although i like most of your songs (as pure music), i think not all fit the pace of a racing game. Songs like "Autumn's Twilight", "Way Up On The Hill" or "Where Did You Sleep Last Night" are too slow and sad for a racing tune (these are also the overly long songs mentioned before).
Also i not see myself driving a Hot Pursuit race, while having Nirvana's "Rape Me" as playback... although there is a certain humor in it maybe - hm.
What i really like are the rock'n'roll tunes. Although these have that 50-60s vibe and probably won't match a modern car lineup...
Faster songs, like "Something Skattish", are a better match-up overall. The menu music is mostly slow and calm, thus a good choice in my book.
Just my thoughts, music is of course always a matter of taste.