Gerard Schwarz’s final program as the Seattle Symphony’s music director, next June, will show him and the orchestra at their best: Schubert’s Eighth and Mahler’s Second. (The “Unfinished” and the “Resurrection”; make of those subtitles what you will.) But it won’t be a sentimental farewell; that came Saturday night. Schwarz’s final season-opening gala offered personally meaningful music: on the second half, Mahler and Strauss, two composers at the center of the big late-romantic repertory he does best.The concert closed lavishly with instrumental excerpts from Strauss’ Der Rosenkavalier, chosen by Schwarz and woven together into a single span that covers nearly all the opera’s high points. Aside from the sheer glory of the orchestra’s sound, what was most impressive was the naturalness and ease of the performance’s rhythmic nuance. However you may feel about Schwarz’s long tenure with the SSO, this is the sort of thing that can only come from a group of musicians who know and can flexibly respond to one another well.Denyce Graves was the mezzo-soprano on hand for Mahler’s four Songs of a Wayfarer. Her voice is both dusky and penetrating, which is maybe not as attractive a combination as you might imagine, and a little rough at the top of her range. The music on the program’s first half was even closer to Schwarz’s heart; a work by him and one written for his son Julian, an excellent cellist and Lakeside School alum now studying in Los Angeles. The wonderfully beguiling Cello Concerto by SSO composer-in-residence Samuel Jones was clearly written to take advantage of what in my observation is Julian’s particular strength: the hyper-focused intensity he can bring to fast music (when warranted). The many whizzing “Flight of the Bumblebee”-ish passages in the finale, so perfectly calculated to achieve maximum impact with just this sort of intensity, couldn’t have been coincidental. The Concerto is brief (20 minutes), but packed with ideas and generous with tunes; darker rather than lighter in mood; richly orchestrated but never overwhelming as a frame and complement to the soloist.Schwarz led off the evening with his own The Human Spirit, a choral/orchestral setting of the Aaron Copland quote carved into the Union Street side of Benaroya Hall. It opens and ends with the chorus (members of four local youth choirs) and strings creating a calm nimbus of sound while harp and vibraphone pick out isolated notes, like stars in a hazy sky; in between, the text is set to a tune that curls extravagantly–and rather daringly, considering Schwarz is writing for young singers–alongside a luscious layer cake of strings. The harmonic language seems to waver dreamily between Mahler and Barber–two streams, flowing together, the Central European romanticism of his ancestors and the mainstream American romanticism of his homeland and career.