Saturday night's IRIS Orchestra concert at the Germantown Performing Arts Centre showed once again the extraordinary ability of these musicians to showcase diversity and skill.

The guest artist was Augustin Hadelich, performing Mozart's "Violin Concerto No. 4" with the technical grace he's become known to deliver. He was here last year with IRIS performing an understated Mendelssohn's "Violin Concerto," but his return this weekend was triumphant, a vigorous expression of Mozart's bright composition.

Hadelich crafted the performance meticulously, rather like wrapping each note in glossy paper and tying on a perfect bow before delivering them to the audience. It was razor sharp, yet with plenty of passion, including exquisite work on the cadenzas.

The Mozart would have been satisfying enough, but Hadelich encored with the notorious "Paganini Caprice No. 24," fiendishly difficult but gloriously effective if the violinist has the virtuosity. He did, memorably so.

The orchestra started out the concert with Respighi's gorgeous "Trittico Botticelliano," three tone poems in tribute to Botticelli artworks. Maestro Michael Stern led the orchestra in these expressive, elegant pieces that so successfully embodied the beauty of another art form.

After intermission, IRIS played Robert Beaser's "Folk Songs" for String Orchestra, Harp and Timpani, a fascinating collection of five works composed in 2007 and utterly American in outlook and expression. Beaser pulls from folk heritage -- from hoedowns to Leadbelly -- and yet remains fully original. The piece titled "Ground O" is a heartbreaking remembrance of 9/11 that never becomes maudlin.

Closing the concert was the orchestra in full Mozart mode again, playing the composer's "Symphony No. 28 in C Major," with riotous strings and strong, even performances from all sections.