MARLBORO — Over the weekend, Marlboro Music Festival opened its 68th season with two concerts that justified its place as one of the most important in the world. Emblematic of the high level of performance was Aaron Copland’s 1950 Quartet for Piano and Strings Saturday evening. No “Appalachian Spring,” this three-movement work used challenging harmonic and rhythmic language, yet there were references to the popular Copland. The expert performance by Marlboro veterans, pianist Cynthia Raim, violist Sally Chisolm, violinist Stephen Tavani and cellist Matthew Zalkind, resulted in a compelling performance of this rich tapestry. Because of the excellent playing, it is easy to forget that this is a chamber music school for young professional musicians rehearsing and performing alongside veterans. While performances vary in success of interpretation, the level of execution matches or excels any festival. Most illustrative of this concept was Saturday’s performance of Schumann’s Piano Trio in D minor, Op. 63. Violinist Soovin Kim, co-artistic director of the Lake Champlain Chamber Music Festival, was joined by pianist Andrew Hsu and cellist Brannon Cho in a performance that was youthful but excellent. While it lacked the gravitas and nuance of seasoned artists, the playing was able, beautiful and spot-on musically. Approaching the concept from a different angle was Sunday’s “Spanisches Liederspiel (Spanish Lyric Scenes),” Op. 70. Four fine young singers — soprano Kristina Bachrach, mezzo-soprano Kara Dugan, tenor Miles Mykkanen and baritone Simon Barrad — sang beautifully and effectively, together, in duet and alone, coached and accompanied by Marlboro lieder expert Lydia Brown. Notable were Bachrach’s dramatic delivery and Mykkanen’s expressiveness. There was an unfortunate tendency among some, playing Mozart, Beethoven and Schubert, to add their own take on the composers’ rhythms. In music of the Classical era, this romanticism not only ignores the composers’ specific intentions, it usually makes — and made — the performance boring. There were some very memorable moments within pieces. Violinist Eunice Kim delivered the lyricism exquisitely in the slow movement, Larghetto, of Mozart’s Piano Trio in B-flat Major, K. 502, Saturday. On Sunday, clarinetist Bixby Kennedy, cellist Allessio Pianelli and Raim on piano gave the slow movement, Adagio, of Beethoven’s Clarinet Trio in B-flat Major, Op. 11, a deep expressiveness and an irresistible warmth. Unique was Carl Nielsen’s 1914 “Serenata in vano.” Described by the composer as a “humorous trifle,” it’s a delightful hodgepodge with jazz and klezmer-like flavors. Although completely disciplined, Kennedy on clarinet, bassoonist Keith Buncke, hornist Trevor Nuckøls, cellist Judith Serkin and bassist William Langlie-Miletich had a great time with it. And so did the audience. After 67 years, Marlboro remains the world’s “ivory tower” of chamber music, where musicians have as much rehearsal time as they wish. And the results show it — results they share with the rest of us. Marlboro Music Marlboro Music Festival presents chamber music concerts July 14-Aug. 12 at Marlboro College’s Persons Auditorium, 2582 South Road in Marlboro. Concerts are at 8 p.m. Saturdays, 2:30 p.m. Sundays, plus 8 p.m. Fridays, Aug. 3 and 10. (Programs are announced a week in advance.) Tickets are $15-$40, $5 for canopied seating Sundays; for tickets, information or schedule, call 802-258-9331, or go online to www.marlboromusic.org.