Here is a website that has probably the biggest downloads of almost every Sonic soundtrack there is. All the links at SOAH (Shadow of a Hedgehog) are/should be free. There are also no viruses, malware, or spam. And, they also offer free lyrics too.
Home page:
Music | SoaH City (
http://www.soahcity.com/music/)
They also have this album for download on their website too. All you gotta do is scroll down to the soundtrack/disc number your looking for. Here's the link for it:
Shadow of a Hedgehog ./ Music ./ Sonic Adventure 2 & Battle (2001) (
http://www.soahcity.com/musicfiles/2001_sonic_adventure2/index.php)
Also, if you don't think the tracklisting is correct, here is a link for the right info:
MJCG-80075 | SONIC ADVENTURE 2 ORIGINAL SOUND TRACK multi-dimensional - VGMdb (
http://vgmdb.net/album/1640)
Hopefully, this helps you in the long run! : D