Getting an empty list for tracks

Thanks, Ned. I've been meaning to address that. Kind of you to spell it out for me. Also good to know that I can indeed pass it that 3-combination bucket. I'll give it a try on the below request that isn't working.

>>> r = requests.get("http://developer.echonest.com/api/v4/song/search?api_key=SREB10QN87HZONHAH&format=json&results=1&artist=Billy%20Idol&title=White%20Wedding&bucket=tracks&bucket=id:spotify")

>>> r.content
'{"response": {"status": {"version": "4.2", "code": 0, "message": "Success"}, "songs": [{"title": "White Wedding", "artist_name": "Billy Idol", "artist_foreign_ids": [{"catalog": "spotify", "foreign_id": "spotify:artist:7lzordPuZEXxwt9aoVZYmG"}], "tracks": [], "artist_id": "AR4T2IF1187B9ADBB7", "id": "SOQXORJ13672C5DC2B"}]}}'