Audiences often think of a string quartet or perhaps an instrumental quintet as standard fare for a chamber music concert, but the Four Seasons Chamber Music Festival started its ninth season with the most intimate of ensemble settings — two duets and a trio — and the listening was no less satisfying than if four or five players had been on stage.

Despite the threat of severe weather, a nearly full Fletcher Recital Hall at East Carolina University welcomed festival artistic director Ara Gregorian, pianist Robert McDonald and cellist Emanuel Gruber for two sonatas for violin and piano and a piano trio. The contrast among the three works was noticeable; the playing on all three excellent.

Gregorian traded his usual viola for violin for this concert, which opened with Janácek’s Sonata for Violin and Piano and closed with Franck’s Sonata for Violin and Piano in A minor, with Beethoven’s Piano Trio in D, Op. 70 No. 1, called the “Ghost” trio, in between.

Janácek’s sonata contains several interesting musical styles and sounds, often played simultaneously. In the opening con moto movement, for example, one could hear a most Romantic piano line played against a more strident violin line, and in the third allegretto movement, two separate and distinct voices could be heard throughout, though at the end a pizzicato passage in the violin is echoed in the piano.

This is post-Dvorák Czech music, though it contains elements of Moravian sources and influences; and Gregorian did a masterful job ending the lovely ballada movement on a soaring sustained high note that faded into the thinnest, driest possible tone.

In the final adagio movement, Janácek’s sonata often sounded more as if it were written for solo piano, and McDonald played with authority and sensitivity. Gregorian’s violin entered fleetingly, in what sounded to be a repetitive six-note figure, and when the two instruments played, the violin frequently seemed to be subordinate to the piano.

Though perhaps not as well known as the “Archduke” trio, Beethoven’s “Ghost” trio still is among his best works for small ensemble. With cellist Gruber providing a rich fullness throughout, the trio was splendid, as all three instrumental voices came together as one. Gregorian and Gruber exchanged lines nicely in the lively opening melody of the allegro vivace movement, and when joined by McDonald, the three musicians produced a surprisingly big musical sound. In the second largo movement, McDonald provided a lovely, long, slow descending run, and later in the same movement — the section of the piece with the moody (even strange) instrumentation that gave the piece its name — the playing by all three musicians built in intensity and emotion, albeit in a sound that one does not normally associate with Beethoven.

Starting slowly, with a nice violin-cello duet, the movement included a low rumble in McDonald’s piano part near the bottom of the keyboard (a motif that came around again a short while later), as well as nervously repetitive string voices. At times, the playing was whisper-quiet; at other times, the strongest fortissimo; it all ended with the softest pizzicato in unison.

The final presto movement returned to more characteristically Beethoven-like scoring, with wonderfully energetic and melodic lines, and both delicate and muscular playing by the musicians. The blend was superb throughout.

The program could have ended quite satisfactorily with the Beethoven trio, but Gregorian and McDonald returned to provide the audience with a performance of Franck’s Sonata for Violin and Piano that could prove to be one of the highlights of the entire season. Gregorian says this is one of his favorite works, and he demonstrated a clear affinity to the gorgeous melody lines for violin. Of course, the entire piece is wonderful, but the glorious final allegretto poco mosso movement, with its simply stated canon-like exchange between piano and violin, could have been played by itself, without the other movements, and the audience would have been satisfied.

So much music from just four hands! McDonald’s score calls for considerable strength, as well as subtlety, and Gregorian was able to immerse himself completely in his part. We usually see him seated as part of a trio, quartet or quintet, so it was interesting to see how he played standing up. He throws himself as energetically into his music while on his feet as he does when seated, with a near-crouch here, and a tiptoe there.

The other movements, by the way, received no less excellent a reading. The forceful tension in the opening of the second allegro movement balanced nicely with the measured stateliness of the solo piano opening and subsequent ascending violin figure in the third recitative-fantasia movement, and both players contrasted forceful playing in the movement with a delicate touch, too.