Priming the pump of musical and emotional flow for its South Pacific tour, the Mormon Tabernacle Choir sang a sampler from its tour programs on Friday night for a large Tabernacle audience (ncluding many mayors of U.S. cities, here in convention) who gave the singers a standing, cheering sendoff.

The choir led with "The Hymn of Praise" Op. 52 by Mendelssohn - actually a kind of cantata, which the composer cast as part of his Second Symphony. Its big, affirmative opening chorus, "All that have life and breath, sing to the Lord" leads to smaller choruses, solos and duets, including the majestic chorale, "Let all men praise the Lord" and ending with a splendid full-out chorus, "Ye nations, offer to the Lord."Friday's performance seemed a collection of parts that have not yet entirely plugged into the flow. Yet one feels that with a little more seasoning and repetition under exhilarating tour conditions, the work will coalesce. Each singer needs to concentrate, not just on singing the right notes, but in projecting the message of praise.

Soprano JoAnn Ottley delivered her customary clarity and tonal beauty, and John Prather's tenor was both lucid and pointed. Heidi McKay addeded warmth to "I waited for the Lord," an oft-excerpted duet for two sopranos.

(`Unconquerable" by Robert Cundick will be reviewed in a report on tour.)

Turning to choir favorites, the singers were in their element with a fine blend, relaxed command of dynamics and extraordinary fluidity of style. Grieg's lyric "How fair is thy face" is becoming a signature piece, and "O My Father" appealed in an unusual arrangement. Copland's sassy "Ching-a-ring chaw" (omplete with a little Appalachian mouth-harp twang) and Luboff's "Deep River" gave a taste of Americana, and Flor Peeters' "Jubilate Deo" added powerful, golden sonorities.

The Children's Prayer from "Hansel and Gretel," sung with a charming innocence and simplicity by the women, and the virile Pilgrim's Chorus from "Tannhauser" for men do not come across as old chestnuts in this context, but as immortal gems of song that promote the spirit of this choir - the feeling of permanence and security, of the best outcome being possible and even probable as cares and worries evaporate away.

It is perhaps this sense of a solemn, steady tread in the universe, this confidence that uncomplicated goodness and rightness will surely prevail, that has made the choir such an enduring attraction with all manner of people. When all is said and done, it will likely be the deeply felt heartsongs the choir gives that will linger longest in the memory of those whose lives they touch on this tour.