14. A method for synthesizing a new musical audio output from a first musical audio input and a corresponding first musical score, comprising using a computing device to: receive a first musical audio input and a corresponding first musical score; align the first musical audio input and the corresponding first musical score; construct a database of audio samples from the first musical audio input and the corresponding first musical score by using the alignment of the first musical audio input and the corresponding first musical score to segment the first musical audio input and the corresponding first musical score into a set of frames representing notes of the first musical audio input and the corresponding first musical score; receive a second musical score; segment the second musical score into a sequence of frames representing notes of the second musical score; identify a separate set of candidate frames from the database of audio samples for each frame of the second musical score; compute a match cost for matching each candidate frame to each frame of the second musical score; compute a transition cost from each match candidate for a given note of the second musical score to each match candidate for the following note of the second musical score; identify an optimal path through the candidate frames relative to the computed match and transition costs; construct a musical audio output by sequentially concatenating the candidate frames corresponding to the optimal sequential path; and construct a third musical score corresponding to the musical audio output wherein the third musical score is a MIDI score.
14. A method for synthesizing a new musical audio output from a first musical audio input and a corresponding first musical score, comprising using a computing device to: receive a first musical audio input and a corresponding first musical score; align the first musical audio input and the corresponding first musical score; construct a database of audio samples from the first musical audio input and the corresponding first musical score by using the alignment of the first musical audio input and the corresponding first musical score to segment the first musical audio input and the corresponding first musical score into a set of frames representing notes of the first musical audio input and the corresponding first musical score; receive a second musical score; segment the second musical score into a sequence of frames representing notes of the second musical score; identify a separate set of candidate frames from the database of audio samples for each frame of the second musical score; compute a match cost for matching each candidate frame to each frame of the second musical score; compute a transition cost from each match candidate for a given note of the second musical score to each match candidate for the following note of the second musical score; identify an optimal path through the candidate frames relative to the computed match and transition costs; construct a musical audio output by sequentially concatenating the candidate frames corresponding to the optimal sequential path; and construct a third musical score corresponding to the musical audio output wherein the third musical score is a MIDI score. 16. The method of claim 14 wherein the musical audio input and the first musical score represents at least one of: a user selected rendition of a particular song; user selected renditions of a set of particular song by a particular artist; user selected renditions of a set of particular songs corresponding to a particular musical genre; and a user selected rendition of a particular song performed by a particular instrument.