I don't know... the theme seemed a little thin, and the fill was often strained. Like ARIOSE (64A: Melodic)(?) and THEMAMBO (39A: Tito Puente specialty) - how often is the article included in an answer? But in other areas, it was fine. I liked COINAPHRASE (12D: Be inventive with language) and EDENPRAIRIE (25D: Minnesota city SW of Minneapolis so named for its fertile soil). Something just put me off. Sometimes it's hard to tell just what does what.
Favorite clue: 45D: Keep it in the family? (INBREED) Runner up: 7D: Ship that was double-booked? (ARK).
That's all for today. I've gotta get to work!
I loved INBREED. Just another example of a racy NYT puzzle clue/answer. Of course, other than that, my favorite was 49A Square root of -1, e.g. IMAGINARYNUMBER. I'd never heard of ARIOSE, but got it, and never heard of EDENPRAIRIE, but got it, too. It seemed fine, but I agree that the article shouldn't be included in the answer. Seeing ITZHAK was nice.