This effect has been in use for all woodwinds and brass instruments for centuries. It involves vibrating the tongue while blowing a note as if rolling the syllable r. It was initially a classical effect which has not been used much in mainstream jazz, but has been used in R & B saxophone playing, notably by King Curtis and Lee Allen. Some people find it difficult to do the R rolling, in which case it may be possible to adapt the uvular flute fluttertongue to the saxophone.