General   (General discussion, talk about anything.)

That's basically a tuner, I have had many, invaluable tuning a guitar or stringed instrument, The best of them clip to the guitar head and tune from the resonation of the guitar which, dosn't pick up the sounds in the room/hall/background, most have a button to switch from ' instrument to background' so it can pick up notes in the room, Very handy if you want to know the key of a song on the radio,