A category of user interface seen on some synths in which a single knob or slider is used for all parameter editing and adjusting. Some mechanism, often involving menu diving, allows the performer to select the parameter to be edited, and then the single knob or slider is used to make the change. Synth manufacturers use one-knob interface designs to reduce cost, since the panel control devices are often the most expensive components in a synth. However, one-knob designs are the bane of performers; they make on-the-fly patch editing during performance impossible, and even "offline" patch editing is cumbersome due to the multiple actions necessary to access and edit a parameter. Additionally, the "one knob" is often actually a rotary encoder, which often suffer from reliability issues.