The album, set for a September 21 release, is part of an ongoing series of fundraising efforts by Townshend for the Chicago-based child abuse treatment center. The collection was culled from recordings made at Towshend's benefit concerts for the charity in 1997 and 1998 at the Chicago House of Blues club. A two-track bonus CD featuring Vedder and Townshend performing together at the 1997 benefit show will be included in the album package.

Vedder and Townshend were scheduled to perform together on Wednesday's edition of ''Late Night with David Letterman,'' which taped prior to the evening's showcase.

According to the Five Horizons report, Vedder joined Townshend for half of the evening's 14-song set, including a rendition of Pearl Jam [ tickets ]'s ''Betterman,'' which featured Townshend on backing vocals and guitar.

In recent weeks, Vedder has performed with members of the band C Average at scheduled shows in East Troy, Wisc., and in Hollywood, Calif., and at surprise shows in Chicago, Il., Encinitas, Calif., and Olympia, Wash. The Olympia show, performed two weeks ago, featured only vintage Who material.

Pearl Jam is expected to return to the studio in September with producer Tchad Blake to begin work on their next album, according to the semi-official Rumor Pit web site. The album's release in 2000 is expected to be followed by a worldwide Pearl Jam tour. In the mean time, the band will perform together at this year's edition of Neil Young's Bridge School Benefit concert in October.