Considering its relatively small size and its much-ballyhooed youth drain, Jerusalem has an impressively fertile electronic music scene. And thanks to the Summer Nights Festival (AKA Chofshi BaKayitz, "Free in the Summer"), you can get a crash course in the musical bips 'n' bleeps that are young Jerusalem's soundtrack. Performing Friday afternoon at the Yellow Submarine are sampleman Terry Poison, electro-rockers Kitzu,  avant-garde electro-funkers Radiotrip, electro princess Onili and breakbeat/trip-hop collective J.Viewz.