Light-driven tone

Four photodiodes, four notes, one Arduino. The Uno runs the sketch in the Arduino IDE: it reads the light on A0–A3 and drives the speaker from D2, D4, D7 and D8. Edit it, upload, and listen. Hold 1–4 to play by hand.

Lamps

Distance to the windows 300 mm

Music

Recording

Hear it through the lamps 100% LM386 volume knob 8%

Room and circuit

Room light 200 lx Light source 2.5 V reference

Black tubes over the sensor windows

Readout

Sounding: —
Reference node: —
I·r² / cos θ, lamp 1: —
Board: —

C4 E4 G4 C5 2.5 V

The scope shows the speaker after the LM386, as the sketch's pins make it. Drop an audio file on the page to follow it. Violet wires are the 2.5 V reference, red 5 V, black ground.

Laying out the bench…