Abstract: In a method of preparing an audio disc by writing music in an additionally recordable optical disc, a specific TOC is first written in a lead in area (LIA) of the additionally recordable optical disc. Thereafter, the music to be recorded is written in a program area of the additionally recordable optical disc.

Abstract: A method of centering a read/write head of a magnetic data storage apparatus on a desired track comprises steps of defining an inside reference track and an outside reference track on the magnetic disk, each of which being recorded with (a) a first servo control data at a center thereof, (b) a second servo control data retarded in time corresponding to a predetermined rotational angle of the disk with respect to the first data at a position offset towards either one of the inner side of the disk and the outer side of the disk by a half width of the track, the predetermined rotational angles being different in the inside reference track and the outside reference track, and (c) a third servo control data retarded from the second data at a position offset towards the other one of the inner side of the disk and the outer side of the disk by a half width of the track.