Adding to a recent question on learning by heart. I tried learning the national anthem of Ireland, Amhrán na bhFiann, by heart, working backwards from the last line - "backchaining" it.

It certainly works. Next time I had reason to sing it, everyone started off strongly:

Sinn na Fianna Fáil,
Atá faoi gheall ag Éirinn

but by the time we were at:

Le gunnai-scréach faoi lámhach na bpiléar

there had been a considerable falling-off. And there were few indeed who knew the second-last line, though the last one:

Agus canaigh Amhrán na bhFiann

came in with a crash.

So it seems to me that though this method is a pain in the ass when you're doing it, it really, really works in practice. It was a couple of weeks since I'd been practising, and I sang the National Anthem today in the car (possibly to the surprise of others heading to the beach) and was word-perfect.

So if you want to learn a tune or its words, that's certainly a good way to do it.