Seventh String Software - Producers of Transcribe!, software to aid the transcription of music from audio form. Includes features to slow down the music without changing the pitch and a spectrum analysis feature to help work out hard-to-hear chords. Site includes details of features, screenshots, reviews and an evaluation version to download. [Windows, Mac, Linux]
Sing & See - Voice training software for singers providing real-time pitch and spectrogram displays
SmartMusic Studio - [Win - Mac] Catalogue of accompaniments, subscriptions and community functions. For woodwinds, brass, and vocalists.