The Temptations, one of the most popular American music acts of the past 20 years, showed last night at the Warner Theatre why they have endured with grace and class.

The group, opening a three-night stand before a large, enthusiastic audience that included D.C. Mayor Marion Barry and his wife, Effi, deftly moved through nearly two decades of widely varied material without sounding false or out-of-date. Originally a singing group in the classic do-wop style of the late 1950s, the Temptations have expanded their repertoire and styles so they can do show tunes, pop standards and disco numbers.

Only two members -- Melvin Franklin and Otis Williams -- remain from the classic Temptations group of the mid-1960s, the one that recorded such hits as "My Girl," Beauty's Only Skin Deep" and "Get Ready." However, Dennis Franklin's hoarse, gospel-tinged voice is even better than that of David Ruffin, and Glenn Leonard of Washington easily covers the high tenor songs once handled by Eddie Kendricks.

Most of the group's set was from its more recent albums, including two works from its latest release, "Power." The most popular segments, though, might have been two looks backward: a clever, chillingly accurate set of songs originally done by other vocal groups, and a spritely medley of the Temptation's own hits. The group's flashy, athletic dance steps, a mainstay since its beginning, continually delighted the audience.

Melba Moore, the opening act, offered a slick, Vegas-style set with several fine moments, notably her interpretation of the Beatles' "The Long and Winding Road" and Larry Graham's "One in a Million." Moore, an original cast member of the musical "Hair," may well have placed the final nail in the coffin of the Age of Aquarius with her disco-fied version of the title song.