Developing good intonation in beginning string orchestra: Note Twins

In order to help students listen to their intonation, I teach them about note twins.  The first note twin they learn is open D, and high D - we talk about how they are not 'identical' because one is high and one is low, but they have the same sound - when played together, you can tell when they 'match'.  We listen and adjust to make sure those two notes sound the same - like when twins wear the same outfit.

 After some basic finger exercises to strengthen the pinky finger (L.H. pizz, finger taps on the fingerboard), we learned 4th finger A's on the D string.  Students were quick to understand that there is an identical note twin - open A.  They were immediately able to adjust their fingers and match their pitch to the open A - especially after I showed them how to swing the elbow to the right to help the pinky reach.  For the cellos, I taught them that they also had a A note twin - and we learned how to shift to 4th position on the D string and play an A with the 1st finger.  My young cellists loved to feel 'advanced' and I believe it is never too early to make these connections on the fingerboard.

I feel that students are able develop quality intonation more quickly when they know about 'note twins' and frequently practice matching identical notes, or notes in different octaves like open
D and high D.