Formidable but wholly invitational, Stop Time is an impressive time capsule of high-potency NYC free jazz. On the track “Untitled III,” the trio of drummer Barry Altschul, double bassist David Izenzon and clarinetist Perry Robinson bring the goods and then some on this 1978 previously unreleased live performance. The players were progenitors of the ’60s free jazz and ‘70s loft …