MARC21       006c'01-02  Form of composition
     Values: 
             an   Anthems
             bt   Ballets
             bg   Bluegrass music
             bl   Blues
             cn   Canons and rounds
             ct   Cantatas
             cz   Canzonas
             cr   Carols
             ca   Chaconnes
             cs   Chance compositions
             cp   Chansons, polyphonic
             cc   Chant, Christian
             cb   Chants, Other religions
             cl   Chorale preludes
             ch   Chorales
             cg   Concerti grossi
             co   Concertos
             cy   Country music
             df   Dance forms
             dv   Divertimentos, etc.
             ft   Fantasias
             fm   Folk music
             fg   Fugues
             gm   Gospel music
             hy   Hymns
             jz   Jazz
             md   Madrigals
             mr   Marches
             ms   Masses
             mz   Mazurkas
             mi   Minuets
             mo   Motets
             mp   Motion picture music
             mc   Musical revues and comedies
             mu   Multiple forms
             nc   Nocturnes
             nn   Not applicable
             op   Operas
             or   Oratorios
             ov   Overtures
             pt   Part-songs
             ps   Passacaglias
             pm   Passion music
             pv   Pavans
             po   Polonaises
             pp   Popular music
             pr   Preludes
             pg   Program music
             rg   Ragtime music
             rq   Requiems
             ri   Ricercars
             rc   Rock music
             rd   Rondos
             sn   Sonatas
             sg   Songs
             st   Studies and exercises
             su   Suites
             sp   Symphonic poems
             sy   Symphonies
             tc   Toccatas
             ts   Trio-sonatas
             uu   Unknown
             vr   Variations
             wz   Waltzes
             zz   Other