Latino jazz-rockers Ozomatli, bluesman Son Seals, bluegrass ensemble the Del McCoury Band and others will play on the second stage during Phish's two-day festival at Oswego County Airport in Volney, N.Y., this weekend, according to the band's promoters at Great Northeast Productions. Between 50,000 and 80,000 are expected to attend the event. This is the fourth consecutive year that Phish, the improvisational rock quartet, has hosted a weekend summer festival. The previous three were held on decommissioned Air Force bases in Plattsburgh, N.Y., and Limestone, Maine. Other second-stage acts include Boston percussionists Bob Moses and Mozamba, funk trio the Living Daylights, New York cover band Hank Williams' Lonely Cheating Hearts Club Band and rock band the Slip. More information on the event is on Great Northeast's website (www.greatnortheast.com).