How can I get a track ID from a track URL using the SoundCloud API?
Since the SoundCloud API is indefinitely not accepting new registrations, here's one alternative solution. This URL will provide you with a wide/short embedded player:
https://w.soundcloud.com/player/?url= + URL of track
Example: https://w.soundcloud.com/player/?url=https://soundcloud.com/chrisbjerken/picking-up-the-pieces
This works for both a single track or a playlist.