A simple self-playing drone synth, primarily intended for meditation purposes but amenable to other uses.

This patch generates a sea of slowly shifting harmonics from two sine wave inputs using Chebyshev functions, and runs the result through a flanger and reverb for additional lushness. Each sine wave can be tuned to notes from a six tone scale (a 1, 3, 5, 9 hexany, providing a just tuned major second, major third, perfect fifth, major sixth, and major seventh). Note that the patch will be initially silent before fading in; be careful to avoid turning the volume too high initially.

Controls:
(use aux to switch pages)
Page 1:
Knob 1: Set ratio for sine wave #1
Knob 2: Set ratio for sine wave #2
Knob 3: Set balance for two voices; 0 = all #1, 100 = all #2. Can be useful to tame the volume if you want one voice to provide some higher harmonics.
Knob 4: Flanger mix

Page 2:
Knob 1: Reverb mix
Knob 2: Reverb dampening
Knob 3: Reverb feedback; this is clipped before reaching 100, but still be careful at higher values.
Knob 4: Reverb spread; adjusting this will create artifacts

Page 3:
Knob 1: Timer time, in minutes
Knob 2: Offset for fine tuning oscillators

Buttons:
Low C: Start timer
Low D: Turn voices on
Low E: Mute voices
Low F: Cancel timer

Starting the timer will momentarily mute the voices before beginning a fade in. A fade out will start at the end of the specified time. Press low D to turn the voices back on afterwards, or E to mute them at anytime.

Acknowledgments:
Many many thanks to @samesimilar for the gen_ext wrapper which made this patch possible. The waveshaper, flanger, and reverb are externals compiled from gen~ patches. Thanks to Graham Wakefield and Gregory Taylor for the excellent Generating Sound and Organizing Time book and their work on Gen~, and additional thanks to those who I might be forgetting.