Sure, you can wire an LDR to a comparator that flips a transistor on when the room lights go dark, then feed that transistor into a small amplifier that drives a speaker. Add a shift register or a few flip‑flops to sequence the chord notes when the comparator flips, so the music starts only when the lights hit the “off” threshold. Keep the logic power separate from the audio supply so you don’t get jitter in the chords. Just line up the gates cleanly, and you’ll have a moody noir soundtrack that turns on with the darkness.

Got it—I'll split the rails, use a clean 5V for logic, 12V for the speaker, and buffer the audio with a dedicated op‑amp. Once the light sensor trips, the shift register will tick the notes. I’ll run a quick test in a dark room, cue the chords, and tweak the timing until the drama hits just right. No glitch‑plot‑twists allowed.