It's a cliche that the world is shrinking. As Gene Santoro sees it in his second collection of essays, music is one arena where that cliche takes on a real, but paradoxical, life: while music crisscrosses the globe with ever-greater speed, musicians seize what's useful and expand their idioms more rapidly.

More and more since the 1960s, musicians, both in America and abroad, have shown an uncanny but consistent ability to draw inspiration from quite unexpected sources. We think of Paul Simon in Graceland, blending Afropop rhythms and Everly Brothers harmonies into a remarkable new sound that captured imaginations worldwide. Or Jimi Hendrix, trying to wring from guitar the howling, Doppler-shifting winds he experienced as a paratrooper.

Or Thelonious Monk, mingling Harlem stride piano, bebop, the impressionist harmonies of Debussy, and a delight in "harmonic space" that eerily paralleled modern physics. From the startling experiments of such jazz giants as Charles Mingus, to the political bite of Bob Marley and Bruce Springsteen, we see musicians again and again taking musical tradition and making it new.

The result is a profusion of new forms, media that are constantly being reinvented - in short, an art form capable of seemingly endless, and endlessly fascinating, permutations.

In Stir It Up, readers will find thoughtful but unpretentious discussions of such different musicians as David Byrne and Aretha Franklin, Gilberto Gil and Manu Dibango, Abbey Lincoln and Joe Lovano. And Santoro shows us not only the distinctive features of the diverse people who create so many dazzling sounds, but also the subtle and often surprising connections between them.