10s of thousands of popular songs, dozens of lines per song.

> Although you have to use the same capitalization rules for all passwords if you have any hope of remembering them.

So no additional combinations from that. Your algorithm is simple and common enough that it's possible that an attacker can figure it out from a single leaked password. With one leaked password they've compromised all of your passwords to anything they have the capability of trying a few million passwords on.

You wrote Pooh songs. Not me. There are millions of songs with lyrics. Billions of lines of lyrics. Trillions of combinations that include upper and lower case. Good luck.