For any of those interested the SEGA Blog announced recently the soundtrack to a number of Sonic games have been released via iTunes.
The titles include:
Sonic Adventure Original Soundtrack – 20th Anniversary Edition
Sonic Adventure 2 Original Soundtrack – 20th Anniversary Edition
Sonic Heroes Original Soundtrack – 20th Anniversary Edition
Sonic CD Original Soundtrack – 20th Anniversary Edition
Super Sonic Songs (The Best of Crush 40)
The Works
Sonic Colors Original Soundtrack – ViViD SOUND × HYBRiD COLORS Vol. 1
Sonic Colors Original Soundtrack – ViViD SOUND × HYBRiD COLORS Vol. 2
Sonic Colors Original Soundtrack – ViViD SOUND x HYBRiD COLORS Vol. 3
Source