Approaches for adjusting the recording density of a recording medium in a circumferential direction are disclosed. A hard-disk drive includes one or more electronic components configured to divide a track, of a plurality of concentric tracks on a magnetic-recording disk, into a plurality of portions, and write data to each of the plurality of portions at a recording density that is independent of the recording density used for any of the other portions. Data may be written to a first portion of a track at a different frequency than to a second portion of the same track. The frequency at which data is written may be adjusted for different portions of the same track to allow the frequency to be reduced at certain portions shown to have relatively higher soft error rate while increasing the frequency for other portions to achieve a desired average error rate for the track.