TheBig Band Era, that immensely important decade in American musical history, died shortly after World War II, but big bands did not, though they were no longer the back-bond of popular music. Many of the period's heavyweights - Duke Ellington, Count Basie, Woody Herman, Stan Kenton - continued to work and produce new music.

Postwar jazz, however, was characterized by small combos, and it became difficult for musicians to get big band experience. Hence the emergence of "rehearsal bands," which enables instrumentalists to participate in large jazz ensembles and composer-arrangers to have their [WORD ILLEGIBLE]played. There now are hundreds of these bands - of varying quality - throughout the country, not to mention thousands of high school and college "stage bands."

In a few cases, rehearsal bands composed of top professionals have blossomed into performing and recording units. The best-known of these is The Thad Jones-Mel Lewis orchestra, founded in 1965. The co-leaders, ex-sidemen of Basie and Kenton respectively, assembled the cream of New York's jazz community, many of them busy studio musicians. Word-of-mouth enabled them to obtain a regular Monday night stint at the Village Vanguard, a Greenwich Village jazz club. Sparked by brilliant compositions (mostly by Jones) and in novative ensemble playing, the Jones-Lewis band grew in importance, obtaining recording contracts and making appearances throughout the United State, Europe, Japan and the Soviet Union.

The latest Jones-Lewis album, "Live in Munich" (Horizon SP-724), was recorded during a 1976 European tour. Though three of the five selections have been recorded previously, the sidemen on this album are almost all different from those on the original recorded versions, providing some interesting comparisons.

"Live in Munich," while not the group's finest album, generally meets the high standards expected from Jones-Lewis. Solo highlights include a furious minor-key blues excursion from pianist Harold Danko on "Mach II"; thinking-man's funk from the late tenor saxophonist Gregory Herbert on "Morning Reverend"; cornetist-arranger Jones' feature on Ellington's "Come Sunday"; and soprano-saxophonist Jerry Dodgion's sly blues on "Central Park North." The rhythm section - Danko, bassist Bob Bowman, and drummer Lewis - is precise and full of fire.

The Los Angeles counterpart of Jones Lewis is the Toshiko Akiyoshi-Lew Tabackin big band. The Japanese-born Ayiyoshi has lived in America since the mid-'50s, end until she and her saxophonist-flutist husband put together an orchestra five years ago, she was known mainly as a minor league be-bop pianist. With her ensemble, she has displayed considerable promise as a composer.

TA-LT's fifth album, "Insights" (RCA AFL1-2678), displays both the strengths and weakness of their approach. The strengths are impeccable ensemble execution, excellent soloists (including Tabackin, alto saxophonist Dick Spencer, trombonist Bill Reichenback, and trumpeter Bobby Shew), some gorgeous wood wind scoring, and unique integration of tradition Japanese music and jazz. The major deficiency is Akiyoshi's limited ability when she turns to more conventional big band jazz. "Studio J" and "Transcience," for example, are bland pieces that could have been hacked out by far less talented arrangers.

The most ambitious effort is "Minamata," a suite dedicated to a Japanese fishing village affliicted by mercury poisoning. There is some haunting writing in the opening section, but the band soon segues into a boppish "blowing session," mostly on the chords of Harold Arlen's "Get Happy." This is overlong segment badly damages the work's unity and emotional impact, despite an effective ending using Japanese vocalists.

All told, this is a fine orchestra, but Akiyoshi, like the late, gifted Gary McFarland, probably would be more at home writing for strings and wood-winds.

In Las Vegas circa 1967, Hungarian-born vibraphonist Tommy Vig led a big band that rehearsed in the wee hours of the morning after its members had finished playing for casino shows. The Vig orchestra's recordings recently were reissued on "Encounter With Time" (Discovery DS-780), part of which originally was released on an obscure Vig LP called "The Sound of the Seventies."

Vig, who wrote all the arrangements, favored the tradition of such bands as Kenton's and Gerald Wilson's; bold and brassy, sometimes oppressively so. Some of Vig's work could be used with little alteration at background music for a TV police series; not surprisingly, he later moved to Los Angeles to work with the likes of Henry Mancini.

Little of the music on this album is artistically earthshaking, but all of it is well-crafted and performed with flair. The brass playing, expectedly, is particularly impressive. And Vig occasionally displays an impish sense of humor that recalls the orchestral efforts of English jazzman John Dankworth.