an optical disk includes a spiraling guide track embedded in a surface of the disk on either side of which is positioned a different information track . apparatus for both tracking and reading the disk includes a source providing two light beams directed to the disk surface and spaced apart such as to nominally illuminate respective ones of the information tracks and part of the intermediate guide track . detectors are positioned to receive reflected light from the disk to both provide signals corresponding to information on the disk and to track the beams relative to the disk so that they are located properly with respect to the location of the information tracks on the disk .