Time-scale modification (TSM) algorithms have the purpose of stretching or compressing the time-scale of an input audio signal without altering its pitch. Such tools are frequently used in scenarios like music production or music remixing. There exists a large variety of different algorithmic approaches to TSM, all of them having their very own advantages and drawbacks. In this paper, we present the TSM toolbox, which contains MATLAB implementations of several conceptually different TSM algorithms. In particular, our toolbox provides the code for a recently proposed TSM approach, which integrates different classical TSM algorithms in combination with harmonic-percussive source separation (HPSS). Furthermore, our toolbox contains several demo applications and additional code examples. Providing MATLAB code on a well-documented website under a GNU-GPL license and including illustrative examples, our aim is to foster research and education in the field of audio processing.

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A central challenge for a cappella singers is to adjust their intonation and to stay in tune relative to their fellow singers. During editing of a cappella recordings, one may want to adjust local intonation of individual singers or account for global intonation drifts over time. This requires applying a time-varying pitch-shift to the audio recording, which we refer to as adaptive pitch-shifting. In this context, existing (semi-)automatic approaches are either laborintensive or face technical and musical limitations. In this work, we present automatic methods and tools for adaptive pitch-shifting with applications to intonation adjustment in a cappella recordings. To this end, we show how to incorporate time-varying information into existing pitch-shifting algorithms that are based on resampling and time-scale modification (TSM). Furthermore, we release an open-source Python toolbox, which includes a variety of TSM algorithms and an implementation of our method. Finally, we show the potential of our tools by two case studies on global and local intonation adjustment in a cappella recordings using a publicly available multitrack dataset of amateur choral singing.

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