I’ve gotten an early start on a long day’s driving. It is dawn on the plains of west Texas and as the sun pops its first bright blast over the horizon, Schubert’s Trout Quintet plays on the car stereo.

Its first chord is also a bright blast, beginning like a sunrise, with a skyrocket of an arpeggio on the keyboard that bounds out like that first instant blaze as the edge of the sun explodes on the horizon.

And when the quintet’s first melody breaks free, the arpeggio is joined by the string bass descending to rock bottom. It’s like the unfolding of a musical universe. It’s almost like getting out of bed, stretching your arms up over your head and planting your feet firmly on the floor.

I often find myself whistling along with the music when I’m driving, but with the Trout, I find myself singing along, bellowing like a playful calf.

It’s a different thing altogether. The whistling is just a kind of inattentive tagging along with the tune.

The singing, however, is my physical presence in the music.

Bump-bump-bump-bummmmm, I yell out with the string bass.

It is that deep resonance that gives an anchor to the music. It is like the footings of a skyscraper dug 60 feet into the bedrock.

The Texas hill country glows in the first rays of the sun, each rolling rise of earth catching the light like the drapery on a Greek statue.

There are a few low sunrise clouds, but the sun enters underneath them and the road is so empty, they just undulate as they run up over the hills. There is nothing on the highway for miles, just the occasional transfer truck that you pass.

What gives the Trout its phenomenal sense of emotional rightness is its constant balancing of the upward and downward motion of its melodies, often at the same time, like the bass and piano at the outset.

It’s not often in life that the emotions coincide in such a perfect sense of morning, light, a new day, optimism and hope.

Such is the Texas daybreak; such is the Schubert. It is a sunny quintet, with hardly the whisper of a shadow in its five bright movements. Even the minor-key variation in the fourth movement is dispelled with a major chord — “I was just playing,” its composer seems to be saying.

Yet, the Trout is an anomaly among Schubert’s major compositions. He wrote it when he was only 22 and it spreads sunshine from beginning to end.

Through most of his best music — the late piano sonatas, late quartets and the great C-major string quintet — there is a strain of despair that is heartbreaking. Even in his short piano pieces, beloved of amateurs for a century and a half, there runs a vein of deep melancholy that shades even his happiest moments.

For soon after he wrote the Trout, Schubert knew he was going to die, and to die soon. He had contracted an incurable syphilis, and it left him an outcast. He was dead before he was 32.

That knowledge, along with his poverty and his habitual sense of isolation and loneliness, give the dark tincture to his mature music.

And even the Trout gives expression — although in the most oblique way — to the melancholy that was constitutional in the composer: The earlier song he had written, also called The Trout, was the basis for his variations in the fourth movement of the quintet. The song tells the story of a bright, wily trout — “who gaily shoots past me like an arrow” — who then gets caught by an “cold-blooded” angler. The poet laments the loss of such a happy, bright fish. It is a miniature exposition of the theme, “Et in Arcadia ego.”

Somewhere east of Balmorhea, sunflowers begin showing up on the shoulders of the highway, great yellow clumps of them — sunshine growing from the roadside dirt.

I drive along in the shade under a cloud, but the sunlight rings the horizon with the tawny sand color of dry grass. I am an audience in the shade, but the spotlight is on a stage in all directions.

The rays of the sun break through the clouds in the north, making lines like rain hitting the ground.

There are lots of birds — finches, and swallows and swifts — darting around in the air over the road. I’m one of them.