Real-Time Music Analysis for the Performer
Ingo R. Titze, William J. Strong · The Journal of the Acoustical Society of America · 1972
Waveform, pitch, dynamics, and 32 harmonic components of a tone with a specified nominal pitch are displayed on a computer-driven CRT. The rate of display is approximately 10/sec, thus presenting essentially real-time analysis. The nominal pitch and the expected pitch deviation are specified by the performer. The pitch deviation can range from a quarter step to a whole step above and below the nominal pitch. The performer can visually adjust his average pitch, monitor his vibrato rate and range, check his dynamics, and observe his spectrum while he sings or plays into the microphone. As an additional feature, the spectrum may be averaged over any specified time interval. The spectrum is obtained by taking a 64 point FFT over a single period of the waveform. The period is determined by sweeping the pitch over the specified range and selecting the best value on the basis of the minimum of a one-cycle average of the waveform and a “fractional period correlation” of adjacent cycles. The present system is comprised of a 30-kHz A/D converter and a PDP-15 computer system with associated graphics.