Many notable synths have the ability so sync oscillators. One oscillator will restart the period of another oscillator, so that they will have the same base frequency. It produces a distinct type of sound, harsh but musical. The timbre can be altered on the synched oscillator by varying its frequency input.
Its used famously in that lead in darude sandstorm for example, but many other songs feature it as well, current pop styles use sync in a lot of bass noises.
Every time the master oscillator's cycle repeats, the slave is retriggered, regardless of its position. If the slave is tuned to a lower frequency than the master it will be forced to repeat before it completes an entire cycle, and if it is tuned to a higher frequency it will be forced to repeat partway through a second or third cycle. This technique ensures that the oscillators are technically playing at the same frequency, but the irregular cycle of the slave oscillator often causes unnatural timbres.
I was surprized the synth didn't already have this feature within it. amSynth is the only thing ive found linux wise that is capable of synced oscillators surprisingly enough.