Johnny Mathis serenaded a full house Saturday with the Buffalo Philharmonic Orchestra in Kleinhans Music Hall.

“A sold-out Kleinhans is a beautiful thing,” announced BPO Associate Conductor Matthew Kraemer, presiding over the concert’s first half.

And it was. All you need is Mathis. What did he sing? Did it matter? His voice is a wonder of the world. You just sit and admire it.

What we heard Saturday was pretty much what we heard the last few times Mathis came to town, give or take a few numbers. He was best in the songs he sang against the simple backing of a combo anchored by a guitar. You could understand him best in that setting. Against the backdrop of that guitar, he sang an exquisite “Shenandoah” and his heartrending hit, “The Twelfth of Never.”

When the orchestra kicked in, Mathis often was drowned out. Apparently, no one adjusted his volume. Some of the material, too – a loud Brazilian medley, for instance – was entertaining enough but did not properly employ the beautiful qualities of his voice.

With Mathis, plain and simple, you want ballads and sensual songs. He is 77 and his voice is as miraculous as ever. It allows him to take a simple approach, singing the song as written. Give him a gorgeous song, and the results are thrilling.

The lovely Borodin melodies from “Kismet” were, as always, a highlight. It was a special delight to hear “The Sands of Time,” based on the melody of the eastern caravan heard in “On the Steppes of Central Asia.” Mathis captures that arabesque quality so gracefully. He brought the same magic to the chromatics of “Laura,” one of his signature songs.

“When I Fall in Love,” which began the evening, was full of tenderness. “The Days of Wine and Roses,” sung against sleepy drums, and “Misty” – no Mathis concert would be complete without them. (Classic, that wonderful moment in “Misty” when Mathis sings that a thousand violins begin to play, and the BPO violins surge on cue.)

It’s always a treat to hear the old jukebox hits – “Chances Are,” “It’s Not For Me to Say” or “Gina.” “You Make Me Feel Brand New” was a crowd pleaser, sung against a great twanging accompaniment from the assembled musicians. “99 Miles From L.A.” had a breathless intensity. Mathis knows how to step into a song and give it atmosphere.

You find yourself marveling at how Mathis handles the microphone. He doesn’t expend a lot of power, but he gets that vibrato across perfectly, and he shapes his words and syllables with care and enjoyment. You are always aware you are hearing a master at work.

He is unapologetic about singing the old songs, which he knows inside out. He needs no music, no lyrics. He is always dead on, and he is master of the stealth key change. A few times during the night, he pulled that trick where he pulls the pitch out of the air, starting the song solo and waiting for the orchestra to come in.

Mathis sang a long and generous second half, without a break, and he received multiple standing ovations. As Kraemer said, it was a beautiful thing.

The first half of the concert was, too. We heard a sultry medley from Cole Porter’s “Kiss Me Kate,” a tribute to Hoagy Carmichael and a jazzy bunch of tunes from the musical “Ragtime.”