Tutorials and Topics - Peabody Computer Music

Tutorial 24Analysis:Oscilloscopedifferent sub-audio beat frequencies, a pattern which only repeats precisely every minute.We have set the number of samples per pixel much lower, so each display representsabout 50 ms. This allows you to see about 10 wave cycles per display.Preset 12. Octaves at 100, 200, and 400 Hz (with different phase offsets), plus oneoscillator at 401 Hz creating beats at 1 Hz.Preset 13. A cluster of equal-tempered semitones. The dissonance of these intervals isperhaps all the more pronounced when pure tones are used. Each display shows about100 ms of sound.Preset 14. A just-tuned dominant seventh chord; these are the 4th, 5th, 6th, and 7thharmonics of a common fundamental, so their sum has a periodicity of 100 Hz, twooctaves below the chord itself.Preset 15. Total phase cancellation. A sinusoid is added to a copy of itself 180˚ out ofphase.Preset 16. All oscillators off.SummaryThe scope~ object gives an oscilloscope view of a signal, graphing amplitude over time.Because scope~ needs to collect the samples before displaying them, and because the userneeds a certain period of time to view the signal, the display always lags behind the signalby one display period. A display period (in seconds) is determined by the number ofpixels per display buffer, times the number of samples per pixel, divided by the signalsampling rate. You can control those first two values by sending integer values in theinlets of scope~. The sampling rate of MSP can be obtained with the dspstate~ object.See Alsodspstate~scope~Report current DSP settingSignal oscilloscope194