Theorist, Mozart scholar and piano improviser extraordinaire Robert Levin dominated last weekend’s eighth Indianapolis Symphony Orchestra season subscription program by engaging in what was common practice in Beethoven’s time: improvising on the spot. For a fair portion of the solo-piano parts in Beethoven’s Piano Concerto No. 3 in C Minor — especially in the cadenzas of its three movements — Levin made them up as he was playing. He’d never played them “quite like that” before and claims he couldn’t duplicate them again — at least from memory. With ISO music director Mario Venzago on the podium, the result of both the collaboration and the improvisation were quite impressive — more so for those aware of what Levin was doing. (Venzago would have done well to announce Levin’s spot-on creative work to the audience prior to playing the concerto. As it was, neither the ISO program booklet nor advance press notice made this clear.) Levin, of course, makes free use of the thematic material Beethoven provides him, just as the composer himself did in his own published cadenzas — those universally played in concert and on most recordings. Otherwise, I found Levin’s piano work to be a bit less than top drawer: His loud passages came across as too loud — almost pounding. His dynamics tended to be strongly layered, which contrasted with Venzago’s smoothly shaped glides from soft to loud, and back. Nonetheless, all performers energized the work sufficiently that both improvised and composed parts sprang to life once again. Venzago concluded the program with a favorite of his, Anton Bruckner’s Symphony No. 0 in D Minor (“Die Nullte”). Completed in 1869 after the Austrian composer’s first and second symphonies, the work struck me as more ingratiating than his so-called “mature” symphonies (4 through 9). First of all, it was shorter, allowing less time to perpetuate Bruckner’s dolorous brass unisons, those never-ending bar and phrase repetitions, all those modulatory shifts in search of a sustaining melody. Still, Bruckner’s wind passages always create a uniquely beautiful effect, and Venzago’s wind ensemble got the most out of them — as well as creating as shapely a whole as is possible with a composer who puts large blocks of tidbits together and calls them a “symphony.” The concert opened with a modern piece that first appeared here a few seasons ago in an Indianapolis Chamber Orchestra concert, William Bolcom’s (b. 1938) Commedia for (almost) 18th Century Orchestra, premiered in 1972. The “almost” derives from the piece’s using a modern grand piano in place of a harpsichord. Written for a small string and wind complement, with three added strings, timpani and two horns on the back riser, the piece is a short pastiche of the late-Baroque style and is amusingly agreeable.