Black is forced to move from the promotion square, to the white square on 7th row, allowing the white king to move to 7th row and protect to the promotion square and then go on to promote the pawn and win.
It was promoted from a technical chess term to a term used in the real world. Zugzwang might mean if you force someone to act, when it is in their best interest not to act.
It is done! I recorded and mixed it myself. It has very bad lyrics (basically the first idea that came to mind and rhymed was good enough). The most basic of chord progressions is used (including only I, IV, V and iv) and a melody constructed around the base note of the chords, which is why the melody sounds like something you heard before. The bridge is fun though as are the key changes and I really like the background harmonies, even if it goes strangely "Sound of Music" in parts.
I recorded it with audacity, a program I never used before (it is really easy to use!) in my bedroom. Guitar and voice were recorded together, because I'm lazy and didn't want to deal with 5 tracks (I had three instead, main vocals and rhythm guitar, background vocals and finger picking and second background vocals). Because of this I couldn't use fancy effects on the guitar or voice, so I just cleaned up some background noise and added a reverb from the bridge onward. During the bridge you hear me tapping to count how long to wait for the background vocals to come in. This is the only attempt at keeping the tempo I made, so the whole thing is a bit wonky.
I'm not quitting my day job.