Audio Pitch Shifting Using the Constant-Q Transform
Pitch shifting of polyphonic music is usually performed by manipulating the time–frequency representation of the input signal such that frequency is scaled by a constant and time duration remains unchanged. A method for pitch shifting is proposed that exploits the logarithmic frequency-bin spacing of the Constant-Q Transform (CQT). Pitch-scaling of monophonic and dense polyphonic music signals is achieved by a simple linear translation of the CQT representation followed by a phase update stage. This approach provides a natural solution to the problems of transients because the CQT has good time resolution at high frequencies while interference between tonal components at low frequencies is reduced. Performing pitch shifting directly in the frequency domain allows the algorithm to process only parts of the signal while leaving other parts unchanged. Audio examples demonstrate the quality of the proposed algorithm for scaling factors up to an octave.
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