Jim Albertson recorded a wonderful album for Folkways that featured folk songs from New Jersey.   I'm not aware of any major studies of New Jersey music, but the Wheaton Arts Center in Millburn is a source. Most folklore collections that I've come across deal more with native arts and stories, very little music.   New Jersey has always been known for immmigrant communities that maintain cultural traditions from native countries. The Scotch-Irish tradition in the Pine Barrens would be dominant.