Henrik von Coler just released a new data set with annotations for monophonic audio excerpts . Three segment classes have been manually annotated:
- note (steady state, sustain)
- transition (transient, release)
- rest (silence, noise, reverberation)
The data set consists of 36 items, excerpts of commercial recordings of solo performances of classical music. It covers the instruments bass, basson, cello, flute, horn, oboe, trombone, trumpet, and violin, and spans several epochs. Although the problem of note-level segmentation is assumed to be solved for monophonic music, non-percussive instruments with weak transients, recordings with larger amounts of reverberation, and notes with large intra-note variations still pose a problem to concurrent approaches. This makes this data set a valuable complement to existing data sets.
More details can be found in the accompanying paper  and on the web site for the data set here.
 Coler, H. v.; Lerch, A.: CMMSD: A Data Set for Note-Level Segmentation of Monophonic Music (2014), Proc. of the AES 53rd International Conference on Semantic Audio, London, UK