getID3() is a PHP script that extracts useful information from MP3s and other multimedia file formats. It extracts information like the play time, bitrate, and resolution from the following file formats: MP3, Ogg Vorbis, WAV, AVI, Matroska (MKV), MPEG-1 video, Windows Media (ASF, WMA, WMV), RealAudio & RealVideo, Monkey's Audio, FLAC & OggFLAC, VQF, Speex, Musepack (MPC), AAC, AU, VOC, AIFF, OptimFROG, WavPack, LiteWave, LPAC, RKAU, SZIP, Shorten, Quicktime, NSV, MIDI, ZIP, ISO9660, TTA, PhotoCD, BMP, PNG, GIF, and JPEG. It parses information from ID3v1, ID3v2, Ogg Vorbis, Lyrics3 v1 & v2, RIFF (AVI, WAV, CDA, CART, BWF), APE, ReplayGain, PNG, and GIF tags, and can write ID3v1, ID3v2, APE2, FLAC, and Ogg Vorbis tags.
Scheme Note is a Scheme-like music file format and MIDI conversion tool. It takes a text file, which is a representation of a song, loosely tied to a MIDI-like event structure, and outputs a corresponding MIDI file. It is hand-editable for simple songs, and should be very easy to parse for a GUI.
The MusicBrainz client library (also known as mb_client or libmusicbrainz) is a library for developers that wish to add MusicBrainz metadata lookup capabilities to their applications. It calculates CD Index IDs and Relatable's acoustic fingerprints, and looks up the metadata associated with the calculated IDs.