As pianist Andrew von Oeyen acknowledged his Omaha audience Friday night, his demeanor reflected the finely honed assurance with which he had applied the broad palette of keystrokes Johannes Brahms demanded of him. One might even say that von Oeyen barely broke a sweat as he and the Omaha Symphony presented Brahms’ Piano Concerto No. 2 of 1881. But that hardly indicates a lack of emotion or engagement. It instead indicates that the American virtuoso, still only 31, brings a seemingly effortless command of the piano and its capabilities to the concert stage..von Oeyen visually illustrated an authoritative quality sought by many a keyboardist. Whether storming through series of chords, gliding through arpeggios or coaxing sweetness out of quiet passages, his fingers barely seem to leave the keys. The slow third movement of the Brahms concerto especially epitomizes the title of the symphony’s weekend program: “Piano Romance.” With a deft, feathery touch, von Oeyen realized his instrument’s full potential to enthrall its listeners.