is first set on the frequency that you want (440 hz in principle but some instruments demand a slightly higher or lower a hz or two) and from the setting, the device indicates by a red light if the note is false, if it is just green with amplitutude + and - through so that we can really pay closer to the correctness; use is easy, you just ring the rope, the device analysis and the arrow shows the frequency
on the advice of my teacher, I also bought the microphone that can fit on a harp for example; as there are about forty string grant is very convenient! we put the microphone in the harp, the tuner next to you and we have both hands free to tune the instrument