When I was younger, I was an obsessive mixtape maker. This pastime was my first to be rendered anachronistic by rapidly advancing digital technology, and so I remember it with pleasure. In the kitchen, my family had a tall black structure with irregularly placed shelves, one of which held a combination cassette player, radio, and phonograph—sort of a dunce’s corner when it comes to current music technologies. When the weather warmed and school days became a thing of the past, I would become preoccupied with the making of mixtapes for drives to my grandfather’s house in Cape Cod.

I would load a favorite tape into Tape Player A and a blank cassette into Tape Player B. Inevitably fast-forwarding to midway through my favorite song, I’d back up to the beginning, and record the track onto the new tape. As it recorded, I’d listen and think about the trip to come. One March, I even collected my favorite summer traveling music and stashed it away until summer so, after such anticipation, it would feel all the better when I listened to it with the windows down.

I think that everybody does this personal categorizing on some level. Wake-up music is not the same as break-up music, just as work-out music is not going-out music. Of all the songs within my own summer genre, renowned slide guitarist Derek Trucks’ cover of “Gonna Move” by Paul Pena is perhaps the epitome of summer music.

The only official recording of the Derek Trucks version is a "Bootleg" from a show at Georgia Theatre. Trucks starts the progression timidly—building from a muted root, to a slightly more wild second, to an unleashed fourth, and back to a slightly more defiant root. The bass and drums kick in, and an organ sweeps the band into a jaunty clip. The group rides this chord progression while lead singer Mike Mattison recounts Pena’s simply told tale of growing up and moving out. The chord progression reflects the theme admirably—each iteration builds upon the last, as if every ascent gains slightly more ground in an ever forward shuffle. The song is always leaving—moving away from the root with evident joy.

Derek Trucks is simultaneously one of the greatest live improvisers and one of music’s most timid stage presences. As a slide guitarist, he wears a glass cylinder on his finger that enables him to play in-between notes, so when he slides into a note he hits exactly every tone that precedes it. Trucks begins each phrase with the hot, crunching noise of his slide ascending to the proper note, and his riffs are characterized by a reliable progression along a tonal spectrum: they begin as harsh, indiscriminate crunches, and then move closer and closer to pure, tender single notes, often gaining slight vibrato towards the end. Each phrase is then answered by a companion—more or less the same idea with one alteration, picking up on the previously established pattern and mutating it slightly.

Though each note is born of many, his early riffs are comprised of single notes, not chords. As the solo reaches its peak, the organist plays successively higher inversions of the chords, and Trucks moves higher and higher up the neck. Mattison belts the chorus, and Trucks quotes the first half of the melody before suddenly dropping away from it to slide into an unexpected, almost gospel chord that sounds like an impassioned, harmonized hum. The song comes to an abrupt halt, but Trucks keeps playing, his guitar crunching and sighing. As the residual band noise fades, his guitar rides a single strum to a breathless low note. Then it rises in a sliding chord, as the bombastic introduction to the Looney Tunes theme song, and the band returns for one last celebratory hit.

This song perfectly fulfilled a certain common criterion on my playlists. A friend of mine once observed that you can hear someone smile when they sing, and, less frequently, when they play an instrument. It’s this intangible sound that Trucks’ rendition of “Gonna Move” so clearly embodies—an openness, a hope, a confident glee. The song is successful because of its infinite regression: At the broadest level, its lyrics pose a theme of leaving with the hope of a better life. On the minutest level, Trucks’ guitar solo is built of many small departures. No note is simply played—all are suggested by an approach that seamlessly becomes another departure. The song’s joyousness lies in its hopeful promise and the perfect unity of all the parts converging to convey the same confident message that is nowhere clearer than in the electric shrieks of Derek Trucks’ Gibson SG. His solos are all journey and never arrival—assertions of build and anticipation over climax; the joy of leaving in hope over staying in despair.

—Columnist Benjamin Naddaff-Hafrey can be reached at bhafrey@college.harvard.edu.