I saw this question just earned the "Tumbleweed" badge and I felt bad.
If the tracks are all owned by the same user, you can use this endpoint:
http://api.soundcloud.com/users/{id}/tracks
If you just have a list of tracks, you can use this endpoint:
http://api.soundcloud.com/tracks?ids=123,234,765,456,etc
See the "filters" section of the docs here: http://developers.soundcloud.com/docs/api/reference#tracks
But keep in mind that although the HTTP spec does not impose a limit on the length of the querystring, the default apache settings will return an error somewhere around 4000 characters. That's probably around 400 tracks for this endpoint. Play around with it. Maybe soundcloud has a limit on the number of tracks per query.