Now in its 67th season, Marlboro Music has been many things to many people. As the friend of a long-time participant, I experienced the festival in much greater depth than I had done in my two drive-through concert experiences; I found that the more time I spent there, the fonder my heart grew over this unique, most prestigious of festivals. Violinist Arnold Steinhardt, who spent much of his career as first violinist of the Guarneri Quartet, remarked, “I have the same feeling I had over a half a century ago. The place is inhabited by musical giants….”

The music festival that spawns these giants is the reason people make the drive — usually from New York — to spend the weekend in this little mountain enclave on the grounds of Marlboro College 10 miles from Brattleboro, Vermont. Unlike Tanglewood, there aren’t other amusements, attractions or even many decent restaurants. One goes for the music, and expects it to be great. It invariably is, but when you make your reservations, you rarely have any idea what pieces will be programmed or who will be performing. That is decided a week ahead, and by then there are no vacancies at the inns. So you take your chances just to hear Marlboro musicians. In three recent visits, I have been happy indeed.

The sold-out program opening the season, on Saturday night, featured the Beethoven Quintet in E-flat Major, op. 16, sometimes done in Beethoven’s own transcription for piano and strings, but here done in the much better version, with winds (Mary Lynch, oboe; Tibi Cziger, clarinet; Natalya Rose Vrbsky, bassoon, Wei-Ping Chou, horn). Pianist Biss played each of his many solo turns with astonishing beauty. I resolved to hear him again whenever he is in Boston — twice for the Celebrity Series this coming season. The horn playing by Wei-Ping Chou, especially in the melancholy melody in the middle section of the slow movement, was unusually gorgeous. This was followed by the Brahms String Quartet in C minor, op, 51, no. 1, with a superb group (David McCarroll, violin; Itamar Zorman, violin; Hélène Clément, viola; and Peter Wiley of the Beaux Arts Trio and Guarneri Quartet). One often hears this piece in a dramatic, more bombastic fashion; this performance was more introspective and lyrical, especially in the third movement. The extensive viola countermelody blended in with the textures of the other three instruments instead of projecting out, making more of a solo statement. Finally, Dénes Várjon, piano, Michelle Ross, violin, and Brook Speltz, cello, played the Beethoven Trio in D Major, op. 70, no. 1. The “ghost” movement was spooky indeed.

We were unusually lucky because our friend enabled us to sit in on several rehearsals. The first thing we noticed was — unsurprisingly — the unusually high level of both sight-reading and playing a difficult Geörgy Kurtág string quartet. Everyone in each of the five rehearsals that I heard seemed able to sing their parts — and others as well — accurately and quite nicely. Most of the “mentors” were well known musicians, while the younger musicians seem to have finished school and were ready to embark on serious careers but were taking the opportunity to enhance their musicianship. Others were taking advantage of their summer off from orchestra jobs to spend time immersing themselves in their real love, chamber music.

An open rehearsal worked on two of Sunday’s pieces, one, a Marlboro premiere. After some 40 minutes working out balance issues in the seven-minute Mozart Adagio and Fugue in C minor, K. 546 (Joel Link, violin, Arnold Steinhardt, violin; Megan Griffin, viola: Judith Serkin, cello), Elliott Carter’s Nine by Five was given its finishing touches. The group (Emi Ferguson, flute/piccolo; Mary Lynch, oboe/English horn, Charles Neidich, clarinet/ E flat clarinet, Natalya Rose Vrbsky, bassoon/ contrabassoon; and Rebekah Daley, horn, muted and not) played very impressively by any standard. After years of trying to persuade Carter to write a second woodwind quintet (the first was written in 1948), clarinetist Neidich succeeded. His interview with Carter affords a good look into the creative process of the composer who finished this piece on December 11, 2009, the date of his 101st birthday.

Marlboro Music has always aimed to blend in older musicians who function as mentors with younger people whom they coach and with whom they play. Many musicians from the early years of Marlboro stayed throughout their lives, starting as youngsters, eventually becoming mentors. Whereas many students who spend their summers at Tanglewood Music Center go on to great orchestra jobs, Marlboro has spawned dozens of chamber music ensembles over the decades — Guarneri, Vermeer, and Cleveland Quartets, for starters. Marlboro’s aim is to allow groups all the time they need to explore a piece of chamber music without the pressure of a concert deadline. One never really knows if one’s group will, in fact, get to perform. Apparently, the joy of rehearsing and analyzing the score and fastidiously trying out new ways of playing each and every phrase is a reward in itself.

Time takes on a special dimension in this magic mountain. (People often speak of the “magic of Marlboro”). Pianist Jonathan Biss said it very well:

“To me it’s clear that Marlboro is really just about time. More specifically, it is about the idea that time is the most precious commodity, and the most important ingredient in a musician’s life. … I realize that I have learned more from some of my rehearsals (at Marlboro) — not just in the groups that ‘clicked.’ but the ones with protracted discussions about a single phrase which ultimately led to no definite conclusions, and certainly not to a performance — than I have from scores of concerts I’ve played that went off without a hitch.”

Marlboro has four more weekends of concerts. If you love chamber music, you should call or go online to make sure seats are available. The hall has beautiful acoustics; you can sit anywhere and hear well. You will be richly rewarded. I cannot wait to return.

Susan Miron is a book critic, essayist, and harpist. Her last two CDs featured her transcriptions of keyboard music of Domenico Scarlatti.