More than ever, the Philadelphia Young Pianists' Academy, now in its sixth year, is attracting boldface names for its dead-of-summer festival, not just with master classes by elder statesman Gary Graffman, but with mid-career recitalists such as Simone Dinnerstein.

On Wednesday, Dinnerstein revisited Bach's Goldberg Variations some 16 years after launching her relationship with this monument in the keyboard literature — then guided and presented by Philadelphia's Astral Artists — that led to her international best-selling recording of the piece in 2007.

Approaching this concert, I returned to that recording so happily that I hoped she hadn't changed too much. But change is more than inevitable here. This huge set of 30 variations show Bach creating his own musical universe by applying his superhuman level of invention to a simple aria melody — and doing so with a kind of abstraction that also allows endless leeway for anyone playing or hearing. Talking about the composer's intentions is difficult here because they were endless. Dinnerstein has always taken a big-piano approach to the piece, and on Wednesday, often had similar interpretive intentions, though expressed differently and with extra flexibility. At least for the first 20 minutes or so.

The repertoire that has passed through her fingers over the years — from her memorable Mozart in Havana project a year ago to lesser-known club appearances with theremin virtuoso Pamelia Stickney — has added to the richness of her Goldberg Variations to the point that the stylistic purity practiced by more historic-minded keyboardists (usually on harpsichord) is light-years away. The length of the performance grew by at least 10 minutes from her recording and the emotional breadth was expanded immeasurably.

Young Glenn Gould (one of Dinnerstein's idols) was described as playing the Goldberg Variations with jet-powered tempos; at times, Dinnerstein seemed rocket-fueled with tempos that were utterly scintillating when nailed, sometimes with heroism suggesting much later composers such as Liszt. You didn't mind, either, when her fingers couldn't always keep up with the speed she established. Never one to imitate Gould — his message was to go your own way, no matter how idiosyncratic — Dinnerstein used slow tempos not as an occasion for microscopic examination (as did Gould) but found intensity amid the musical invention in the music's inner workings. These were some of Dinnerstein's most penetrating moments partly because the variations she chose were ones that aren't so outwardly dramatic and are noticed less in other performances.

Dinnerstein wasn't big on 18th-century-style ornamentation that is often improvised and give even more variety to the Goldberg Variations amid the many passages where Bach asks to make one more pass through whatever music is at hand. Dinnerstein was more inclined to use pianistic color to intensify the repeated passages, making the piece feel even more formidable. Also, she often found an emotional kinship among the variations, creating groups of four or five of them that formed their own cogent, collective identity. All of these elements conspired to remind you that no matter how often you've heard the piece, it keeps growing in stature.

The eight-day festival of concerts and lectures has moved from the Curtis Institute to the Academy of Vocal Arts partly because more facilities are available. The theater's dry acoustics still aren't lovable, but most anything that facilitates the expansion of this festival, founded by Taiwanese pianist Ching-Yun Hu, is for the good.

Information: PYPA concerts continue Saturday. Tickets: $25. www.pypa.info