> Now, 30+ years later, it's a bit rusty, but I can still read it pretty well, and can sort-of understand written Portuguese as well.

I don't want to be picky. But I would not attribute your ability to read Portuguese to your musical background, but to your Spanish. My experience is that most Spanish speakers can read Portuguese to a certain degree and vice-versa. Never having studied French, I was able to read some child comics.