Risky. Dangerous. Scary. A way to break the rules.

We’re not talking about failing to study for your final math test or disobeying your parents. We’re talking about a type of music called jazz.

Some people say that jazz is America’s only true art form. That’s because it began here, hundreds of years ago, in the fields where black people worked as slaves and made up songs to pass time, to express themselves and to keep alive the culture and traditions of their African homelands. It wasn’t called jazz then, but the way the slaves were playing and singing music was different and special.

The music of America’s black people came to be called jazz in the South in the early 1900s; New Orleans is often called the birthplace of jazz. Despite slavery’s having ended in 1865, African-Americans still didn’t have the same rights as white Americans. But jazz was music that both black and white people could enjoy. By the 1920s, jazz was growing in popularity and included influences from Europe as well as Africa.

Jazz has all the elements that other music has: It has melody; that’s the tune of the song, the part you’re most likely to remember. It has harmony, the notes that make the melody sound fuller. It has rhythm, which is the heartbeat of the song. But what sets jazz apart is this cool thing called improvisation. That means making it up on the spot. No music in front of you. No long discussion with your bandmates. You just play.

“It’s more free. It’s more soulful,” says Geoffrey Gallante, 11, a sixth-grader at Stratford Landing Elementary School in Alexandria, Va. Geoffrey is such a good musician that he has appeared at the Kennedy Center in Washington and has been on television lots of times; he has even played with the band on “The Tonight Show With Jay Leno.”

In jazz, Geoffrey says, “it’s easy to express your emotions. In classical, . . . you get the sheet music and you read it top to bottom. You’re more focused on technically making it perfect. . . . In jazz, your main focus is . . . being creative and using your imagination.”

It’s not that jazz songs don’t have recognizable melodies. They do, but that’s just a small part of it. In jazz, a melody begins a song, but then each musician will take turns improvising, playing all kinds of crazy notes: high, low, long, short, gravelly and clear.

The performers who are not soloing are playing quietly in the background, or comping, short for accompanying. Then at the end of the song, the melody returns. Improvising is what makes a jazz song different every time you hear it, unlike any pop song you hear on the radio.

Another thing that sets jazz apart is its approach to rhythm. Think of “The Star-Spangled Banner.” When you hear that song, it probably doesn’t make you want to tap your foot. There are no rhythmic surprises, or what is called syncopation, in most presentations of “The Star-Spangled Banner.” Jazz musicians, on the other hand, “swing” notes, which means they change the length of notes, holding some longer and making others shorter.

Gallante was 4 years old when he picked up the trumpet. Now he practices three hours a day, mostly classical pieces. But what he really loves playing is jazz. It’s the spontaneity of jazz — that means there’s no planning ahead of time — that he really loves. He can walk into a club that he has never visited, with guys he has never seen, and just play.

“The [band leader] says, ‘What do you want to play, and what key?’ [I] can get up there and have a blast. With classical, you have to plan everything. You need to practice. . . . It’s a whole big production. With jazz, you just walk up and you say, ‘Hey, I want to do this. . . . Let’s go.’ “