In writing this piece, I wanted to make room for — and highlight — the trombone’s multiple qualities.

What emerges in the first movement is the instrument’s funny, almost ironic, character accentuated by the glissando parts. But the second theme, which follows, is full of melancholy and passion.

In the second movement, the still atmosphere gives birth to a deeply dramatic melody—in contrast to a second, lighter theme, aerial and imbued with hope.

The whimsical element comes back in the ...