Knob or handle that maintains the flow of water. Rough-in not included.
This is the controls that allow you to determine how loud or soft you can play your music. Powerful headphones and speakers will give you a finer control of volume than cheaper ones. The MP3 player will also have a maximum output capacity, usually listed in Decibels.
Just like on a stereo system, this adjusts the guitar's volume. However, a guitar can have more than one volume control. Usually, there's a single volume control, even if there are two or more pickups. Some guitars have a separate volume control for each pickup, and may also then have a master volume control that sets the overall loudness of the guitar.
A gain control of an amplifier.
A wheel or button on the faceplate of a hearing aid or on a remote control utilized by a hearing aid wearer to increase or decrease the instrument's gain.