1x push button switch
1x 100 ohm resistor
1x 220 ohm resistor
1x NE555 timer chip
1x mini speaker
1x 1uf-100uf capacitor
1x 2.2uf capacitor
1x 9v battery and clip
1x bright white or blue LED
Some perfboard, solder, soldering iron, and wire
Step 1: The Basics
Step 2: The Schematic
The photocell value doesn't matter, just use one that can get enough light.
I tried using a 4.7uf capacitor in place of the 100uf capacitor and it worked fine. My point is that this is a flexible circuit. Don't be afraid to substitute parts to find what works best for you.
I would use a 2.2uf capacitor for the 1uf-10uf capacitor.
The speaker doesn't have to be 16 ohms, but it works the best.
PLEASE use a bright LED. It will make your life so much easier (and give the synthesizer the best sound).
Build this on a breadboard before you put it on perfboard.