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