No matter what one thinks of Frank Sinatra the person (and there are good reasons to resent his reactionary, macho, overbearing attitudes), one should never let those feelings get in the way of enjoying Frank Sinatra the singer. Sinatra is quite simply one of the very best American vocalists of the 20th century (ranking right up there with Elvis Presley, Ella Fitzgerald, Aretha Franklin, Bing Crosby, Ray Charles, Al Green, Billie Holiday and Bessie Smith). Baby-boomer audiences, who resented Sinatra the person's snide attacks on rock-and-roll, should listen to Sinatra the singer and hear the qualities that had such a crucial impact on Presley, Charles and Green.

Sinatra turned 75 on Dec. 12, and to wish him a happy birthday, two record companies released CD boxed sets of his music. "The Capitol Years" (Capitol) includes 75 songs from 1953 though 1962 on three compact discs plus a 70-page booklet; "The Reprise Collection" (Reprise) offers 81 songs from 1960 through 1986 on four CDs plus a 36-page booklet. These two boxes skim the cream off one of the most glorious careers in American popular music and serve as an excellent introduction to the Sinatra canon.

Sinatra's career divides neatly into three parts, each section connected to a different record company. After singing with the Harry James and Tommy Dorsey bands, Sinatra signed his first solo record contract with Columbia in 1943 and stayed with the label through 1952. Those early recordings, nicely anthologized in 1986 on the four-CD boxed set "The Voice -- The Columbia Years, 1943-1952" (Columbia), made the Sinatra of the curly black hair, dimpled boyish cheeks and bow tie a pop star. These were pop songs, and Sinatra presented new love and lost love as uncomplicated issues made thrilling by his lustrous voice.

By 1952, however, Sinatra's records had stopped selling, and he seemed like one more washed-up pop star, over the hill at 36. He had been reduced from playing theaters to playing clubs, but Capitol Records took a chance on him and signed him to a new contract in 1953. The first Capitol session with Axel Stordahl, Sinatra's primary arranger at Columbia, was more of the same, but musical history was made on April 30, 1953, at the second session. Stordahl had accepted an engagement with Eddie Fisher; the preferred replacement, Billy May, was on tour and unavailable. So Capitol paired Sinatra with a young arranger named Nelson Riddle, who had enjoyed enormous success with Nat King Cole's "Mona Lisa."

The first song Sinatra and Riddle tackled was Harold Arlen and Ted Kohler's "I've Got the World on a String," and it introduced a brand-new Sinatra. It begins with quiet, intimate strings beneath Sinatra's offhand confession; the brass enter blasting, and the vocal knocks out the song's declaration of new love with a jaunty assurance that swings aggressively. This was a more mature, more relaxed music that was less concerned with stylized formality than with personal authenticity.

If Sinatra's Columbia recordings had been inspired by Bing Crosby's pop crooning, the Capitol recordings were influenced by Billie Holiday's softened, bluesy jazz confessionals. It was this injection of African American blues into Sinatra's Tin Pan Alley music that transformed it from skillful entertainment to enduring art. The blues weren't obvious in Sinatra's music -- his repertoire remained show tunes and pop standards -- but they were the catalyst that made his syncopated rhythms, his blue-note harmonies and his instinctive lyric readings so special.

New technology introduced the 10-inch long-playing album during Sinatra's early years at Capitol, and the singer became the first pop artist to record "concept albums" conceived as unified song suites. The pioneering effort was "In the Wee Small Hours" and the best was "Only the Lonely," both ballad collections shaped by Sinatra and Riddle to reveal the weary, lonely side of the blustery American male epitomized by the singer. It was this dialectic of the tough guy and tender lover coexisting in the same body that created the dramatic tensions in Sinatra's richest music. These albums are so good, in fact, that you may not be satisfied with the sampling on "The Capitol Years"; you may find you need the whole albums.

By 1961, Sinatra the singer had become such a profitable industry that Sinatra the person decided he should be in charge of the business. He founded his own record label, Reprise (which he sold to Warner Bros. Records for a million dollars in 1963), and began a maddeningly uneven period that contained some of his best work ever as well as some of his most forgettable.

Among the highlights were two studio albums and one live one with the Count Basie Orchestra (and Basie arrangers Neal Hefti and Quincy Jones). These are brilliant recordings, with Sinatra swinging as hard as Basie's brass section but also singing with the playful economy of Basie's own piano playing, and you should own them in their entirety. There were productive reunions with Riddle and 1 1/2 wonderful albums with the Brazilian composer Antonio Carlos Jobim.

Sinatra, though, had absolutely no aptitude for songs written after 1960, and his later albums were filled with awful compositions by hacks like Rod McKuen, Alan and Marilyn Bergman, Jake Holmes and Norman Gimbel. For that reason, "The Reprise Collection" is more useful than "The Capitol Years," since the Reprise albums include so much more junk to be filtered out.

"The Reprise Collection" contains eight previously unreleased songs plus two songs never released in the United States; "The Capitol Years" contains one unreleased song, one alternate take and three songs only available on a rare, mail-order-only album. None of these rarities are essential Sinatra, but they should satisfy the fanatics who have had to make do with inferior bootleg versions. The Reprise booklet has essays by novelist William Kennedy and critic David McClintick but infuriatingly incomplete discographical information (what albums are these songs on?). The Capitol booklet features personal remembrances by daughter Nancy Sinatra, purple prose by critic Will Friedwald and thorough, helpful track-by-track information from Pete Kline.

Whether you buy these boxed sets or opt for the original albums (buy any Sinatra album associated with Riddle, Basie, Jobim or Billy May), you owe it to yourself to own some Sinatra. Forget the public persona; forget musical boundaries; this is great American popular music, as important as anything by Duke Ellington or Bob Dylan.