# Time-domain harmonic scaling

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Time-domain harmonic scaling (TDHS) is a method for time-scale modification of speech (or other audio signals), [1] allowing the apparent rate of speech articulation to be changed without affecting the pitch-contour and the time-evolution of the formant structure. [2] TDHS differs from other time-scale modification algorithms in that time-scaling operations are performed in the time domain (not the frequency domain). [3] TDHS was proposed by D. Malah in 1979. [4]

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In Western music, the term chroma feature or chromagram closely relates to the twelve different pitch classes. Chroma-based features, which are also referred to as "pitch class profiles", are a powerful tool for analyzing music whose pitches can be meaningfully categorized and whose tuning approximates to the equal-tempered scale. One main property of chroma features is that they capture harmonic and melodic characteristics of music, while being robust to changes in timbre and instrumentation.

## References

1. Richard V. Cox; Ronald E. Crochiere; James D. Johnston (February 1983). "Real-time implementation of time domain harmonic scaling of speech for rate modification and coding" (PDF). IEEE Transactions on Acoustics, Speech, and Signal Processing. ASSP-31 (1): 258–272.
2. Moulines, Eric & Jean Laroche. (1995). "Non-parametric techniques for pitch-scale and time-scale modification of speech" (PDF). Speech Communication. 16 (2): 175–205. doi:10.1016/0167-6393(94)00054-e.
3. D. Malah, R.E. Crochiere, and R.V. Cox. (1981). "Performance of transform and subband coding systems combined with harmonic scaling of speech" (PDF). IEEE Transactions on Acoustics, Speech, and Signal Processing. 29 (2): 273–283. doi:10.1109/tassp.1981.1163547.CS1 maint: multiple names: authors list (link)
4. David Malah (April 1979). "Time-domain algorithms for harmonic bandwidth reduction and time scaling of speech signals" (PDF). IEEE Transactions on Acoustics, Speech, and Signal Processing. ASSP-27 (2): 121–133.