Here is the full list of all 38 Riff Racer - there are Race Your Music achievements.
Score more than 100,000 on a song under 3 minutes in length
Smash 30 boxes or more without missing one
Drift more than 16 beats in one manoeuvre
Unlock 20 packs
Drive ALL cars
Reach Driver Level 20
Stay in the super-sync zone for 25 consecutive seconds
Reach Driver Level 15
Drive 100 songs
Beat a friend's ghost
Drive 10 cars
Reach Driver Level 10
Unlock 10 packs
Play a single song 10 times
Play a Hip-Hop/Urban song
Jump more than 8 beats in one manoeuvre
Drive 50 songs
Play a Pop Song
Play a Jazz/Funk/Soul song
Play a Classical song
Reach Driver Level 5
Enter the super-sync zone 10 times in under 40 seconds
Drive 5 cars
Unlock 5 packs
Author 10 tracks
Drive 25 songs
Stay 100% in sync for a whole song
Drive a whole song without hitting a barricade
Author 5 tracks
Drive 10 songs
Race on a song longer than 10 minutes in length
Play a Rock/Metal song
Boost 20 times or more in one song
Author 1 track
Roll more than 4 beats in one manoeuvre
Beat a recommended ghost
Play a Dance song
Unlock ALL packs