So what really is good intonation in an ensemble? Pitch matching! I highly recommend that you stop trying to tune every instrument with a tuner and also stop putting the responsible for tuning the instruments on yourselves. Put it where it belongs, and that is on the students, but first you must teach them what in tune and out of tune sounds like. I am not saying that tuners are a bad thing, I am just saying that we overuse them. Sticking a tuner up to a student and then telling them they are flat or sharp is not going improve their ability to play in tune.
Once you demonstrate what in tune and out of tune is, then you must teach them what to do. It seems logical that they already know what to do, but from my experience, students do not always know that if they are sharp they need to extend their instrument (loosen the string) or if they are flat they need to shorten their instrument (tighten the string). Plus once they have one note in tune, does that mean that the ensemble will play in tune? Well, of course not, but too often this assumption is made by us and them. Students must be trained to match pitch with the other musicians in the ensemble. They have to be able to make instant adjustments in their embouchure (or finger placement for strings) to play in tune.
We want to strive for beatless tuning. A good visual aid is to have students wave their hands with palms down to the speed of the beats in the sound. Hopefully as intonation improves their hands will slow down. Also, don’t forget to have them tune to a fixed pitch. Making students adjust to a tuner playing a tone will be very beneficial to getting them to understand what they have to do to play in tune. And please remember that the quality of their tone, balance and blend effects intonation greatly. Students need to learn how to play “inside” the sound of the ensemble. If they are sticking out in any way then they need to check their tone, then their intonation, then their balance, and there blend. If they lose themselves in the sound, chances are they are in tune. So please use tuners in moderation and focus on what really playing in tune means in an ensemble, and that is pitch matching.
I also recommend that you check out an incredible new device I have discovered for intonation training. It is the Yamaha HD-200. For more information go to: http://usa.yamaha.com/products/musical-instruments/winds/harmony_director/harmony_director/?mode=model