For violin, I would recommend placing your horizontal guide lines to correspond to a just scale rather than 12-tone equal temperament.<p>Another type of tuning visualization that only works with just-tuned instruments is to have something like an oscilloscope, with the vertical axis connected to a microphone or pickup and the horizontal sweep set to be the same frequency as the root of your key.  An interesting thing that happens is that, for any note that makes a whole-number ratio with respect to the horizontal sweep rate, you get a standing wave.  If it&#x27;s drifting to one side, it&#x27;s sharp, and if it&#x27;s drifting the other way it&#x27;s flat.<p>I experiment with just-tuned guitars, and this is what I do with an old analog oscilloscope to check if my intonation is right.