Marines in the music OccFld provide music to support military ceremonies, official functions, community relations, personnel procurement programs, and troop "esprit de corps." In combat, musical units continue musical functions and augment security on a temporary basis during periods of heightened combat intensity when use of the band in its primary role is impractical. Marines entering this OccFld will receive MOS 5500, Basic Musician. All OccFld 5500 MOSs are assigned and voided by authority of the CMC (MM). Marines enlisting under the Musician Enlisted Option Program (MEOP) may be required to attend the Music Basic Course at the School of Music after having completed recruit training and Marine Combat Training (MCT). Assignment to a Marine Corps Band follows successful completion of the Basic Course. Career Marine musicians may return to the School of Music for advanced technical training or complete the Instrument Repair Course provided through a civilian school. The opportunity to participate in a formal apprenticeship program leading to receipt of Department of Labor Certification of Apprenticeship may be available in some MOSs within OccFld 55.