11:00 - 11:20
An Zhao and James Beauchamp
University of Illinois at Urbana-Champaign
Single Musical Tone Time-Scaling That Preserves Temporal Structure
Sounds produced by linear stretching of nonvibrato single tones fail to retain their microstructure in the time domain. Looping is commonly used for elongation with wavetable synthesis, but this requires careful attention to waveform boundaries. We use looping on recorded musical tones to elongate and crossfading to shorten them in order to control their synthesis duration while preserving their texture. Looping in the time domain was explored, but we found that time reversals at specific time points cause abrupt waveform phase reversals resulting in audible clicks. Therefore, we decided to use the same method on harmonic and frequency envelopes produced by the SNDAN pitch-synchronous phase vocoder [Beauchamp, 2007]. In this case, looping retains continuity of the additive synthesis parameters: amplitudes, frequencies, and phases of the harmonic partials. To retain realism, original attacks and decay time data are preserved. Attack and decay times are automatically estimated by measuring the times where the DB RMS envelope and its average value intersect. For shortening, envelopes are cross-faded between the attack-end and decay-begin points. Thus, the minimum synthesis duration is the sum of the attack and decay times, unless the data during these times is altered. As an application, we have implemented the algorithm in the musical synthesis program, Music 4C, a score-processing program.
Design downloaded from free website templates.