Left Hand Thumb position

Many players are taught to keep their left hand thumb in a fairly stationary position behind the neck of the guitar whilst playing. In some ways it makes sense that in order to stay in position you need to have a reference point which is usually the thumb. The reference point refers to the lateral side to side movement but what about up and down?

Recently, I began experimenting with keeping the thumb more or less directly opposing the tips of my fingers so if I play a note on the 6th string the thumb is up high on the neck, and if I play a note on the first string the thumb is well down on the neck. I have to say that it has given me a new sense of control and flexibility and I have noticed it has also solved some issues in my students Left Hand technique.

You will find that allowing the thumb to move vertically to assist your fingers will give you more power, accuracy and control especially in scale passages