We’ve all had the experience – a jazz band is playing one of our favorites, “I Got Rhythm” or “My Favorite Things” or even “Moondance” – and halfway through the song we say, “Wait – what song is this again?” It’s taken off in an entirely new direction, and suddenly sounds nothing like Gershwin, or Van Morrison for that matter.

In part, that’s because that’s what Jazz Is: Improvisation. From its roots through its heyday and into the modern forms of the music, jazz has always taken the loose approach to melody, and its re-interpretations and spontaneous creative leaps are what makes it so unique in music. And what makes listening to masters like Charles Lloyd (right) so rewarding.

Other musics of the world do include improvisation in their expression – African drummers extrapolate on the rhythmic cycles, gamelan players create a tapestry of sounds on a pre-established melodic pattern. But jazz is unique in its emphasis on individual creativity – the soloist is practically a jazz invention, the guy (or gal) with the horn standing up and blowing his (or her) heart out in music.

But doesn’t that mean it’s all “made up”? Is there any order in the music that gives it shape, regardless of the soloist’s imagination and skill? Of course there is. Traditional jazz is improvisation on a song, and a song is composed of a structure, a melody based on chords played in measures.

This may sound, well, obvious, but it’s only obvious to musicians, who in turn can’t believe that everybody doesn’t “get it.” The chords of a song, and its melody, invariably provide the first run-through of a number on stage or in recording (called “the head”). Subsequent repeats of the song provide the opportunity for musicians to improvise on the melody though the chords that create the structure of the song itself (“playing the changes” in musician’s terms). The elegance or dissonance or success of a solo are rooted in how well, poorly or creatively the musician uses the constraints of the structure to express his individual message.

Among other topics, Billy Taylor defines improvisation in his “What Is Jazz” lectures at the John F. Kennedy Center for the Performing Arts (follow this link  for audio excerpts).  His definition: “Improvisation is spontaneous composition… based on the sense of form, content and language of the song.” In other words, to borrow a classical music term, a jazz performance might be thought of as “Variations on a Theme by Cole Porter,” or Harold Arlen, or Wayne Shorter or Miles Davis, or Joao Gilberto.

All of which makes the final chorus so gratifying – when the band returns from their musical journey and repeats the melody, changed and charged by spontaneous composition along the way, and reveal to us a familiar song made fresh by jazz.

— Christian Kallen

Think you know what jazz is? Leave a comment on our page, “What Is Jazz?”