The circuit was designed to provide a prototype of a metronome circuit utilizing the functions of CA741 operational amplifiers.The operation is of circuit can be considered as astable where it continuously oscillates to different states.
http://www.zen22142.zen.co.uk/Circuits/Music/metro.html
This circuit uses a UM3561 IC to produce four different sound effects.
http://www.hobbyprojects.com/music_sound_special_effects/sound_effects_generator.html
This circuit uses the Holtek HT2884 IC to produce 8 different sound effects.
http://www.hobbyprojects.com/music_sound_special_effects/sound_effects_generator2.html
contains very many guitar effect unit circuit diagrams
http://hem.fyristorg.com/effects/rack_k.htm
How to set up a simple, yet effective, ground system that can be installed in a short period of time with a minimum number of tools.
http://www.hard-core-dx.com/nordicdx/antenna/ground/ground3.html
do-it-yourself.
http://machines.hyperreal.org/categories/do-it-yourself/
http://sound.westhost.com/project64.htm