The New York Pinewoods Folk Music Club is a good resource for info. They'll tell you what's going on in folk music. They can be contacted at www.folkmusicny.org. Greenwich Village is a great area for jazz. The Blue Note is a top-notch jazz club, and often features legendary performers. Lots of really fine jazz at the not-yet-legendary categories, too! You might want to pick up a copy of New York magazine. It lists what's currently happening in the clubs. Several NYC resident Mudcatters here (I'm a NYC fan and frequent visitor, not a resident). They will hopefully spot this thread. An overwhelming number of choices in the USA's most exciting city!

chanteyranger