Phil Lesh [ tickets ] & Friends will augment their summer lineup with special performances from Trey Anastasio [ tickets ] and Mike Gordon [ tickets ], both formerly of Phish.

Ex-Grateful Dead bassist Lesh and his Friends--an ever-changing lineup that currently consists of Joan Osborne, guitarist Larry Campball, keyboardist Rob Barraco, pedal steel guitarist Barry Sless and drummer Jeff Sipe--are set to kick off their summer schedule with an appearance at the June 18 Bonnaroo festival in Manchester, TN. The first headlining date for the band comes two days later, June 18 in Nashville.

Anastasio and Gordon will join the trek June 30 in Raleigh, NC, and will close the show that night. The two groups will alternate closing and opening duties for 10 other shows in late June and early July.

Joining the two ex-Phish will be the Benevento-Ruso Duo, featuring Marco Benevento (keyboards) and Joe Russo (drums).

Before the ex-Phish members join Lesh's tour, a sold-out pair of performances beginning May 18 at San Francisco's Warfield Theatre will be filmed for an upcoming DVD release, according to Lesh's website. An announcement recently posted on the site asked ticket holders to "participate in the revelry and wear your finest festive garb, as there will be film crews inside and outside the Warfield filming and documenting the entire Phil Lesh & Friends concert experience," as well as refrain from taping, which is generally tolerated and even encouraged among fans of Lesh and other Grateful Dead spinoff acts.

Last year marked the 40th anniversary of the formation of The Grateful Dead, which had fans speculating that the legendary band--re-dubbed simply The Dead in the wake of the 1995 death of frontman Jerry Garcia--would mark the milestone by regrouping for a tour, but Lesh's busy touring schedule with his own band likely prevented this from happening, if in fact it was ever under serious consideration.