Over 500 vocalists are catalogued here, spanning a chronology beginning with the earliest commercial recordings and running all the way to present day with stylists like Diana Krall and Frank Sinatra.

Yanow, a longtime professional who has been writing about the world of jazz for more than three decades, has labored intensively to include only those singers he feels truly make the cut. Developing that criteria was not easy: Is Frank Sinatra a jazz singer? Were the early blues singers of the 1920s and the big band innovators of the 1930s also blues singers? And are singers who overlap caberet, world, and rock/pop also jazzers?

Finally, though, the author cut it down to a field of 521 (to be exact). Each entry contains biographical info like birth dates and birthplaces; several author-penned paragraphs detailing style and influences; a quote (not in all in cases) from the artist him/herself; and a Recommended CDs section.

The Jazz Singers: The Ultimate Guide is arranged alphabetically. Here is a sample reading for Billie Holiday:

"One of the most famous of all jazz singers and a living legend by the 1940s, Billie Holiday broke many musical rules. She had a small voice that was subtle yet very expressive and could be heartbreaking in her interpretations."