Chart datum, level of water depth on a nautical chart. Datum or datum point, a (possibly arbitrary) reference baseline or point from which scientific measurements are made (from a Latin meaning of datum as a given, i.e. an accepted fact)
Music directors and composers must guide musicians and singers by preparing musical arrangements and helping them achieve the best possible sound. Musical talent. To become a music director or composer, one must have musical talent.
Many composers have begun their careers as music copyists, either on a freelance basis or engaged principally to assist one established composer. A good music copyist, devoted to this specialized and labor-intensive skill, may establish a comfortable living in his/her craft.