Drum tuning is the process of adjusting the frequency or pitch of a drum. Although most drums are unpitched instruments, they still have a fundamental pitch and overtones. Drums require tuning for a variety of reasons: to sound good together as a kit, to sound pleasing as an individual drum, to achieve the desired amount of ringing and resonance, and to produce the sound that fits the music. Some drums such as timpani and rototoms are tuned to a definite pitch. Drums are tuned by tightening or loosening the tension rods or ropes, which control the tension on the drumhead. Additional techniques such as muffling may also be used to affect resonance.