Vortiene,
You can use song/search with the "bucket=audio_summary" parameter to get audio attributes about your library. Metadata matching may give you multiple matches (e.g. live, studio, album, or acoustic versions with the same title), so you may need to filter or match on durations to be more accurate.
To get precise audio summaries for the local tracks, track/upload is the best way. Yes, you need to upload each track once, but then you have a TR id for each and can get back to attributes and analysis using track/profile quickly in the future. This takes two API calls for each track but is guaranteed to give you attributes for the tracks you have.
David