A song written with the number Pi.
I created a custom metronome of which I took 3 normal beats, and one of 0.1415 times the length of one beat. This is a very short one, and our perception (and my production) feel more like an extended 3rd beat instead of an added short fourth. 
The melody is an 8 bar sequence using the first 32 notes on every beat. 
Besides these notable Pi occurrings, there are way more things where I used pi, like: -delay time, pre delay on reverbs, reverb time, compression ratios, thresholds, etc.

A song from PI - π/4 time | Melody of Pi

pauldavids