Simplify the following text for a Grade 6 native English-speaking person.
Original: Jazz fusion is a musical fusion genre that developed in the late 1960s from a mixture of elements of jazz such as its focus on improvisation with the rhythms and grooves of funk and R&B and the beats and heavily amplified electric instruments and electronic effects of rock . While the term `` jazz rock '' is often used as a synonym for `` jazz fusion '' , it also refers to the music performed by late 1960s and 1970s-era rock bands when they added jazz elements to their music such as free-form improvisation .
Simplified: Jazz fusion began in the late 1960s in the United States .