Here in Australia's first, largest and by most accounts greatest city, the Mormon Tabernacle Choir gave the first of two concerts on Friday night, singing perhaps its best performance of the tour before a capacity audience.

Sydney's justly renowned concert hall is itself a symphony in beautifully joined light and dark woods that create warm, resonant acoustics. Here, Mendelssohn's "Hymn of Praise" fulfilled conductor Jerald Ottley's ideal for it - a cohesive mini-oratorio with choral numbers that glistened easefully, swooping over Mendelssohnian hurdles with energy to spare. Expert soloists JoAnn Ottley, Heidi McKay and John Prather added to a completely satisfying whole.The Sydney Opera House (as the entire complex of hall, opera and drama theaters is called) is an enchanting spot sure to challenge the imagination.

Jutting into the harbor like some winged mythical vessel under full sail, it is equally lyrical by day or by night - gleaming white against the dazzling blue sky and water in morning sunlight, or luminous under pale light by night.

In this jewel of a building, a fit mecca for our tour, the choir encountered several highlights. Philips Polygram Records have taped Friday's concert and Saturday's matinee. For the cover of the album that will result, the singers were photographed on the steps of the Opera House. And on Sunday, "Music and the Spoken Word" will emanate from the hall as well.

The choir has been seasoning down, firming up and singing ever more musically, with increasingly sensitive ensemble, as the tour has progressed and is fulfilling its reputation as Utah's premiere choral ambassador. Indeed, one speculates that (if relieved of daily toil and family concerns) the choir members might wander the globe indefinitely, becoming continually more professional and successful.

One might feel as if he had been wandering indefinitely on this long tour. Fortunately, illness has eased up and most here are in good shape. And luckily, singing days, with usually two concerts a day, have been separated by travel and resting days.

But "to see Australia you have to hop," says the kangaroo on the travel slogan, and hop this choir has, from one highlight to the next. One marvels at their musical and physical self-discipline, their efficiency in loading buses quickly, being on time, keeping quiet when necessary and following directions. And they are never late for dinner!

Concerts in Adelaide's Festival Hall, part of a charming white arts complex beside the River Torrens, suffered from the built-in Monday lag, hence crowds were lighter than usual. However, the general choir consensus was that these were their most effective concerts to that point, and critics responded with enthusiasm.

Everyone fell in love with Perth, a beautiful green city where the Swan River flows into the Indian Ocean - a sort of big-time Brigadoon of wholesome isolation and ambient lifestyle. Here, the farthest away from Salt Lake City that the choir has ever sung, two concerts drew good audiences.

Still to come on this magical sojourn Down Under, the Tabernacle Choir salutes Australia's Bicentennial with two concerts in Brisbane's concert hall on July 4th - United States Day at Expo '88.