Probably most of the time we try to avoid feedback (particularly if wearing headphones) but synth experimenter Simon the Magpie has created his own Feedback Organ based on months of playing with deliberate audio feedback.
His 3D printed case features two sets of holes. On one side they cover a two-watt speaker, and on the other side are seven individual microphones. By connecting them with flexible tubes in various combinations, and manipulating the other controls, you can generate some incredibly bizarre sounds from feedback loops.
Other audio sources can be plugged in to include them in the audio signal path. The instrument includes electronic feedback loops, a classic PT2399 delay and drive circuit for the speaker, and a volume knob, button and switch/latch for each microphone.
Units are available for around $350 (depending on exchange rates and such like) from the Magpie Pedals shop. It’s a really cool concept and implementation — just connecting up elements with clear PVC tube is awesome!
Check out the demonstration video for more: