Kyogu Lee recently announced the defense of his PhD on the music-ir list. The title of his work is "A System for Chord Transcription, Key Extraction, and Cadence Recognition from Audio Using Hidden Markov Models".
Fabien Gouyon pointed me to Alex Loscos’ thesis which was completed recently. The title of his work is "Spectral Processing of the Singing Voice" (abstract and PDF).
Fabien also pointed me to the thesis of Álvaro Barbosa which was completed last year (and which I hadn’t included in the list of MIR PhDs yet). The title of his work is "Computer-Supported Cooperative Work for Music Applications" (PDF).
The music technology group (MTG) in Barcelona is currently by far the most productive MIR research group in terms of completed PhDs. A MTG specific PhD list can be found here.