Target Acquisition vs. Expressive Motion: Dynamic Pitch Warping for Intonation Correction

The purpose of pitch correction is to assist a musician in playing notes with accuracy and precision, without preventing expressive pitch variations. This study presents and examines a new method for automatic pitch correction: Dynamic Pitch Warping (DPW). The analytic formulation of the warping function is derived. In the context of live playing of continuous pitch trajectories, the dynamics of pitch correction must be considered. Methods for triggering and releasing the correction are discussed, and a performance test is conducted. DPW is evaluated in the context of digital musical instruments that are controlled by a stylus on a graphic tablet. The results show significant improvement in note accuracy and precision with the addition of the correction method. Analyses of various types of modulations (including vibrato, portamento, and glissando) demonstrate that expressive pitch variations are preserved by the DPW correction. Perceptual tests show that the effects of DPW correction are well perceived and positively assessed by listeners. The proposed method allows for accurate pitch target acquisition together with preservation of expressive motion, a result that could be extended to other situations that require dynamic trajectory correction.