With its evenings like silk and its vast arbors of lawn and foliage, Tanglewood brings out a poetics of the whimsy – of golden light and self-reckoning. Friday’s Prelude Concert at Ozawa Hall coupled Mozart’s gently mocking Quartet in A for flute, violin, viola and cello, K 298, with Brahms’s deeply personal String Quartet No. 1 in C Minor. Composed for a circle of friends, namely for the family of his student Franziska von Jacquin, the son of a celebrated botanist, Mozart’s Quartet reveals the composer’s love of pastoral idioms and fun. Elizabeth Klein gave her flute a lovely wistful, breathy feel, prompting Bonnie Bewick’s violin, Rachel Fagerburg’s viola and Owen Young’s cello to respond with mock-rustic timbres tinged with silliness, as though sketching an early appearance of the great Papageno character of Magic Flute. What the BSO musicians suggested through their skillful interpretation is that Mozart meant to gently coax his friends to recognize the sweet but inept attempts of less-talented composers and to aspire to a more refined, complex musical realm.

In contrast to Mozart’s subtle wielding of parody to refine our ear, Brahms appropriated the medium of the String Quartet for a soulful self-portrait. Elita Kang on the violin led her cohorts into an urgent, passionate expression of aching desire in the opening Allegro, showing how desire cuts through the soul, tossing us in every direction, mercilessly. She then led the second movement Romanze (poco Adagio) into evoking a sort of haven of grace and relief, before unleashing the Finale Allegro with smoldering longing, infusing the piece with vitality like an inward, hidden Sun. What a revelation! Brahms had burnt many a previous attempt at composing a string quartet before going public with this poignant glimpse into his inner being. The BSO players brought us the fullness of it.

Leon Golub is an astrophysicist at the Center for Astrophysics in Cambridge and has been a lover of classical music for over 50 years.