Gary Giddins is the author, most recently, of "Visions of Jazz: The First Century."

Immense as the jazz library is, you can't really gauge how many blanks need to be filled in until writers come along to fill them. They marked a lot of new territory during the past year, in several categories.

History: Spreadin' Rhythm Around by David Jason and Gene Jones (Schirmer), is an invaluable, largely unprecedented survey of black songwriters who flourished in the years 1880 to 1930, blending theater, blues and jazz, and producing many of our most durable melodies. Though compromised by the straw men it attacks without naming, Richard Sudhalter's Lost Chords (Oxford) is a trove of fresh historical and critical thinking about the contributions of white musicians between the two World Wars.

Biography: The late Peter Pettinger pays homage to a great pianist in Bill Evans: How My Heart Sings (Yale) by focusing on his music, and Alyn Shipton rescues Dizzy Gillespie from the lore of bebop in Groovin' High (Oxford). But the surprise page-turner of the year is Peter Levinson's life of the swing-era star Harry James, Trumpet Blues (Oxford), the cautionary tale of a gifted man who wanted to see the money.

Oral history: Central Avenue Sounds (California) is a vital mosaic of jazz in Los Angeles, compiled by a committee of seven musicians, among them Clora Bryant and Buddy Collette. The art of the interview is exemplified in two surveys of contemporary musicians, Bill Milkowski's Rockers, Jazzbos & Visionaries (Billboard) and Howard Mandel's Future Jazz (Oxford).

Memoir: Selected writings of the most influential figure in American music are authoritatively edited by Thomas Brothers in Louis Armstrong in His Own Words (Oxford). Rosemary Clooney (with Joan Barthel) tracks her journey from the big bands to bland pop to a rapprochement with jazz in Girl Singer (Doubleday).

Reference: The eagerly awaited Biographical Encyclopedia of Jazz (Oxford), by Leonard Feather and Ira Gitler, is, as expected, indispensable.