LETTUCE is (a) the prime ingredient in a salad, (b) a slang for cash, (c) a green herb that can be smoked, (d) a genre-busting six-member musical collective formed in 1992 by four alumni of the prestigious Berklee College Of Music, or (e) all of the above. If you answered “e,” then you’re in on the sheer magic of a band that both feeds the rich history of funk music and combines it with strains of hip-hop, rock, psychedelia, jazz, soul, jam, go-go, and the avant-garde.