WELLFLEET - With a program ranging from classical proportions to romantic excess, the Cape Cod Chamber Music Festival opened its 32nd season Monday evening at First Congregational Church.

The estimable Tokyo String Quartet launched the three-week festival with an insightful performance, offering quartets by Haydn and Ives, then being joined by festival co-director Jon Nakamatsu for the Schumann piano quintet.

The Haydn G major quartet, one of the two "Lobkowitz" quartets that were the last he completed, shows how the great inventor of the medium infused traditional structures with intelligence and subtlety. At least that's how we feel about it. Haydn himself thought his two final quartets a failure, compared with the "new" works (the six Opus 18 quartets) that Prince Lobkowitz commissioned at the same time from a younger upstart named Beethoven.

After Tokyo's solid reading of the piece, we can all agree to disagree with Haydn. The G major breaks no major ground in the basic structure of the string quartet - sonata first movement, slow movement, a fast dance and then a rousing conclusion. But in all of the details, it stands out.

The slow movement, deeply personal, takes a single musical emotion, stated quickly by the first violin, and explores its depths. The surrounding movements, all with a folk or vernacular feel, offer lively interplay in the instruments. Nobody leads, nobody follows, but everyone participates vigorously.

What Haydn built on proportion and wit, Ives creates with tension and texture. Ives' first quartet, subtitled "A Revival Meeting" because it steals from actual and imaginary church hymns, appeals in its directness. It's almost self-explanatory: easy melodies, well structured and, in this performance, knitted together in a way that creates infectious musical cohesion.

Ives could make a quartet, or an orchestra, sound like a marching band playing different tunes - in fact, more than once he did just that, on purpose. This quartet does take an amalgam of songs but stitches them together with unexpected casualness into something beautiful. Only in the final movement does Ives sound like the Ives we expect - all bumptious rhythms and counterintuitive playing. The rest of this first quartet has relaxed, long lines, frequently in unison pairs, of alluringly listenable tunes.

Tokyo, first formed in 1969, still ranks at the top of existing quartets, despite personnel changes through the years. This particular incarnation - Martin Beaver and Kikuei Ikeda (violins), Kazuhide Isomura (viola) and the impressive Clive Greensmith (cello) - has worked together almost a decade now, and the members respond to each other's skill with profound facility.

One measure of an ensemble's confidence comes in bringing unexpected ideas to familiar pieces. With the Schumann piano quintet, written lovingly for his wife, Clara, and certainly one of the most frequently performed chamber works in all the repertory, Tokyo's approach was jarringly unexpected - but provided rewards that can come only from expert interpretation and performance.

The second movement was of particular note. Marked "In the Style of a March," it is often rendered beautifully as a slow, stately processional. Instead, Tokyo attacked the movement, emphasizing the "In the style" aspect and transforming the march into more of a pattern than a mood. It became a rumination, not funereal but thoughtful - a viable but unexpected insight.

With the other three movements full of robust, infectious romantic outbursts, this re-reading of the slow march made sense out of the whole work. Rather than offering a break in the emotional frenzy, the march seemed like just another way of looking at the swirl of passionate excess around it.