It has been a long time since I bought my current tuner (a Seiko Chromatic Auto-Tuner) so I thought I would browse around and see what’s available now. I found lots of tuners and a large range of prices. Unfortunately, what I see most are tuners that only read pitches, without an internal tone generator or sound out port.
So what’s wrong with that? I did, after all write a practice book on how to use that kind of tuner to improve intonation. The problem is that this is only a beginning in the quest to perfect playing intonation. The feedback that a tuner’s readout gives you is only part of the picture, a narrow slice. It’s great for working on consistency, and learning the sizes of scales and intervals, but it can only help so much. In my opinion, what is needed is a tuner that can generate pitches as well as reading them.
By working with a tuner that plays the pitches, you can work on improving your ability to hear when you are in tune or out of tune, so you can function in the real playing world. Tuners are calibrated to an equally tempered scale in which all half steps are the exact same size. Unfortunately, when those half steps are combined into larger intervals, our ears don’t like that rigid equality. Different intervals need to either be expanded or compressed so our ear hears them as being in tune. Are our ears wrong? No, but it would take a long explanation to clarify this and others can do it much better than I can.
Besides the dissonances with equal temperament, the playing conditions, pitch tendencies of different instruments, and abilities of the players all play a part in the ever-moving target of good intonation. A little bouncing light or digital readout will not give you the information that you need to play in tune when you play with others. To learn this, you have to exercise your hearing and your ability to constantly adjust the pitch.
So, in my opinion, when you buy a tuner or download a tuner app, or whatever, get one that will read all the pitches your instrument can play, one that has a display that is easy to read, and one that will sound at least a full chromatic octave; two or three would be even better. It doesn’t have to be expensive, it just has to do everything you need it to do. And leave your tuner at home when you go to rehearsal or a performance. Your attention should be on the music and your interaction with the other players, not on a gadget! Music is for the ears, and is not made with the eyes.