Pianist Oscar Peterson and singer Ella Fitzgerald have performed together often over the past 27 years. But Saturday night at the Wolf Trap Jazz Festival, these two stars each took half of the show. The 56-year-old Peterson sat alone at the piano for the first set; the 64-year-old Fitzgerald was supported by pianist Jimmy Rowles' trio (featuring Washington bassist Keter Betts) in the second set. Both stars applied their legendary techniques and imaginations to reveal new nuances in even the most familiar jazz songs.

Peterson strung his standards together in long medleys. He stated the melodies with a light, swinging touch, then blazed through the chord scales with 16th-note triplets that recalled the great Art Tatum. Peterson also displayed an impish wit as he twisted a song from its expected task. The highlight of his set was "Cakewalk," an original ragtime piece that has a captivating melody and undulating syncopation that rank with the rags of Scott Joplin.

Fitzgerald took a few songs to find her full voice. But once she did, she showed how she can make the best-known songs all her own. She took the nursery rhyme, "Old MacDonald Had a Farm," and reinvented it as a fast bop tune by changing key every verse and by working more and more against the rhythm. On Duke Ellington's "Take the 'A' Train," she jumped back and forth between baritone and soprano falsetto and even imitated a slide trombone solo with her voice. She crowned the show with a fast, spectacular scat version of Dizzy Gillespie's "Cool Breeze."