1. A computer-implemented method, comprising: performing, by one or more computers: applying a transform technique to an input signal to generate a transform of the input signal, wherein the transform is a time-frequency representation with a logarithmically spaced frequency axis; decomposing the transform of the input signal to estimate one or more kernel distributions and one or more impulse distributions, wherein each kernel distribution represents a spectrum of a particular source in the input signal and each impulse distribution represents a relative pitch track for a particular source in the input signal, and wherein each impulse distribution corresponds to a respective one of the kernel distributions, wherein said decomposing the transform of the input signal comprises imposing a prior on each impulse distribution so that each impulse distribution follows pitch expectations of a particular source; and displaying the one or more kernel distributions and the one or more impulse distributions.