Steven Isserlis — iconoclast, pied-piper, gadfly and raconteur of the cello — never stays still, either artistically or in performance. Author of musical books and plays for children, fervent advocate for obscure works of Schumann, explorer of new repertoire and unapologetic user of all gut strings on his instrument (despite their severe limitations), he goes his own way with sincerity and whimsy. Joined by Russian pianist Kirill Gerstein last Friday at the Barns at Wolf Trap, Isserlis delivered with trademark dramatics, his gray mop of hair almost a third performer.

He has played and recorded with a slew of different pianists, but Gerstein seems the first who truly understood how softly he needed to play with this cellist most of the time. Gut strings have a warmer but gentler sound, and in the tempests of the Bartok Rhapsody or the Brahms Sonata in F, Op. 99, the music calls for more power and clarity than Isserlis’s equipment has, particularly on the low strings. His excessive body language highlights the futility rather than compensates. But Gerstein was a model of accommodation; I doubt he has occasion to play so consistently lightly at any other time (he has a big solo career), but he did so here with good grace, clear involvement and admirable rhythmic clarity.

In unaccompanied or quiet lyrical passages, Isserlis showed why he is a world-class artist. In two minor works of Liszt, the colors and lofty imagination in “Romance Oubliée” and the immanent yearning imparted to “Die Zelle im Nonnenwerth” will long linger in my memory. The freedom and artistry in the trio section of the Brahms Sonta in E-minor, Op. 38, and the analogous section of the Op. 99 sonata were also highlights, the two musicians working in perfect tandem to create a richly colored soundscape.

Isserlis had inexplicable difficulty with the tremolos in the first movement of the Op. 99, the (structurally important) rhythms incoherent or inaudible. But for the rest, it was an evening of vital, stimulating music-making.