You were thinking of Gygöry Ligeti's "Poème symphonique"[0] in your last example there. Steve Reich did write "Pendulum Music"[1] where microphones are swung fr

You were thinking of Gygöry Ligeti's "Poème symphonique"[0] in your last example there. Steve Reich did write "Pendulum Music"[1] where microphones are swung from cables over loudspeakers and the feedback goes in and out of phase as the microphones return to stillness. [0] https://www.youtube.com/watch?v=-mUv705xj3U https://www.youtube.com/watch?v=-mUv705xj3U [0] https://www.youtube.com/watch?v=fU6qDeJPT-w https://www.youtube.com/watch?v=fU6qDeJPT-w