Madrid night life for old guy

I'd ask the tourist offices. Those are both large cities; there may even be a brochure available on music venues.

I must warn you about Madrid, though. Spaniards don't seem to sit down to dinner before 10 PM, so nightlife probably runs on an equally late schedule. I suggest also asking about concerts featuring music of the types you're interested in. I remember seeing posters in Barcelona for small-group jazz concerts at churches. They didn't start super late--maybe at 9 or 9:30.

For both places, I would pick up any weekly magazine covering entertainment and choose from among the many options...you can find them once you're on the ground. Much more comprehensive than what you can find on random websites or travel books. Or perhaps look at Time Out (online) guides of each city - they usually list music venues to get you started. I think most nightlife begins pretty late, but don't let that stop you from going (or age for that matter!). There should be plenty of variety of venues and musical genres that will work for you - perhaps you're looking at a sliver of the choices in any given guidebook.

That makes a lot of sense. Thanks for the replies!

I'm a big fan of live music myself so I try to check it out on my trips. There are obviously some specific concerts and such that require advanced planning/tickets (I did this in Istanbul for some performances which were a bit on the formal side), but if you're just looking for informal places that are not likely to sell out, then picking up the local paper will do fine.

I read a number of travel forums. Ones that are city specific may provide suggestion for say, a jazz bar. I have read some for Barcelona that might not be too late. Even if you don't join the forum you can search the forums for possible answers. Otherwise TimeOut would be a valid option.