Tutorials and Topics - Peabody Computer Music

Tutorial 29Processing:Flangedemonstrating how MIDI can be used for realtime control of audio processingparameters.The different examples stored in the preset object are characterized below.1. Simple thru of the audio input to the audio output. This is just to allow you to test theinput and output.2. The input signal is combined equally with delayed versions of itself, using short(mutually prime) delay times for each channel. The rate of modulation is set for 0.2Hz (one sinusoid every 5 seconds), but the depth of modulation is initially 0. Use themod wheel of your synth (or drag on the “Mod Wheel” number box) to introduce someslow flanging.3. The same as before, but now the modulation rate is 6 Hz. The modulation depth is setvery low for a subtle vibrato effect, but you can increase it to obtain a decidedly unsubtlewide vibrato.4. A faster vibrato, with greater depth, and with the delayed signal fed back into thedelay line, creates a complex warbling flange effect.5. The right channel is delayed a short time for a flange effect and the left channel isdelayed a longer time for an echo effect. Both delay times change sinusoidally over atwo second period, and each delayed signal is fed back into its own delay line (causinga ringing resonance in the right channel and repeated echoes in the left channel).6. Both delay times are set long with considerable feedback to create repeated echoes.The rate (and pitch) of the echoes is changed up and down by a very slow modulatingfrequency—one cycle every 10 seconds.7. A similar effect, but modulated sinusoidally every 2 seconds.8. Similar to example 5, but with flanging occurring at an audio rate of 55 Hz, and nooriginal sound in the mix. The source sound is completely distorted, but themodulation rate gives the distortion its fundamental frequency.SummaryYou can provide a continuously varying delay time to tapout~ by sending a signal in itsinlet. As the delay time varies, the pitch of the delayed sound shifts oppositely. You canuse a repeating low frequency wave to modulate the delay time, achieving either subtle orextreme pitch-variation effects. When a sound with a varying delay time is mixed with theoriginal undelayed sound, the result is a variable comb filtering effect known as flanging.230