Boston concert audiences have been blessed over the past few years with the appearance of two entrants in the somewhat amorphous category of “chamber orchestra.” One of them, the Discovery Ensemble, began its third season on October 17, under the leadership of its Northern-Irish conductor Courtney Lewis, at Harvard’s Sanders Theater in a commendably mixed program of works by Bohuslav Martinu, Arnold Schoenberg, and a fellow named Beethoven.

Apart from its three-program public concert season, Discovery spends its time bringing classical programming to area public schools otherwise devoid of it. We wish them great success in this endeavor, and if their school performances are as well thought out and executed as what we heard Sunday afternoon, no concerns of performance quality need impede that success.

We cannot recall a previous live performance of Martinu’s Double Concerto for two string orchestras, piano and tympani. (His work in fact should be programmed more often.) The Concerto dates from 1938, in the tense days of Germany’s annexation of Austria and the Sudetenland part of Czechoslovakia, and the music’s virtually unrelieved chromatic tension well conveys Central Europe’s anxieties. (We were reminded of one of our favorite New Yorker cartoons of the era, wherein a concert-going matron whispers to her companion, “I had no idea conditions in Europe were so bad!”) In this piece, Martinu eschews overt expressionism for a synthesis of neoclassicism and Bartók whose Music for Strings, Percussion and Celesta of 1936 seems influential here. The Martinu, though, is far from a copycat piece.

The division of the strings into two equal and facing units seemed more visually than aurally effective, as the ensembles were less antiphonal than one might expect. The piano part, admirably played by Aaron Likness (without solo billing, likewise tympanist Jeffrey Means), is percussive and, except in the slow movement, generally integrated into the orchestral texture. That slow movement, by the way, with its haunted-cathedral opening employing swirling strings, and its air of quiet unease — its main melody re-emerges at the end of the febrile and martial finale — was to us the compositional high-point.  Lewis kept a clear beat and tossed off an impressive display of body English (Irish?), as his crack band of young performers (not a gray hair onstage) responded with immaculate articulation and dynamic precision.

The first half of the program ended with Schoenberg’s Chamber Symphony No. 1, one of the last works he wrote before taking expressionism past the bounds of classical tonality (the symphony is nominally in E major). This work, for fourteen solo instruments, famously provoked Gustav Mahler to question the viability of so intense a chromaticism. Its four linked movements all use the same musical materials and so are best regarded as constituting a single, articulated musical event, especially when there are not great changes in tempo or meter.

The greatest challenge to a conductor of this piece, apart from keeping everybody together through Schoenberg’s elaborate counterpoint, is to preserve some semblance of balance; with only one player to a part it is obvious that the strings are disadvantaged, and indeed, in the first two movements especially, the violins and viola had some trouble making themselves heard. The slow movement and finale saw a distinct improvement. Like almost any Schoenberg score, this one placed enormous demands on the players because of the compact form in which it imposes extreme expressive requirements, and resulting difficulty of the parts. Here both the audience and Lewis expressed their approbation for the nearly total success of the enterprise.

It raises an eyebrow, perhaps, to think of a chamber orchestra rendition of Beethoven’s revolutionary and overwhelming Eroica symphony, and yet a band of forty-some was probably about right for 1803. Discovery Ensemble makes no pretense to “original instruments” or “historically informed” status, so with modern instruments it can produce the volume this work needs to succeed. And succeed it did, after its fashion. Let’s say at once what everyone wants to know about an Eroica performance: the horns (Whitacre Hill, David Vaughan, and Sarah Sutherland) were just fantastic in their sectional solo in the scherzo.

This was clearly a young person’s Eroica: brisk tempi, dramatic dynamic shifts, theatrical body language — not your deeply reflective mitteleuropäische exegesis. Lewis is a master of dynamic control and pacing, although, especially in the first movement, his rapid beat left some phrase endings gasping for air. The funeral march left nothing to be desired to our ears, and the finale overcame the biggest issue we have always had with this symphony, which is that in the majestic restatement of the theme just before the coda, Beethoven may have exceeded the capacity of his instrumental forces to sustain a full sound when his simple melody was stretched out. We don’t know how he did it, but Lewis achieved here a glowing, rounded sonority that has eluded many of his elders. Bravo.

Vance R. Koven studied music at Queens College and New England Conservatory, and law at Harvard. A composer and practicing attorney, he was for many years the chairman of Dinosaur Annex Music Ensemble.