In the previous two posts I wrote about the common problem of over covering the embouchure hole that detracts from producing a great sound. The correlation of the right hand thumb position on the flute and the coverage of the embouchure hole is often overlooked by flautists.
I encourage the three point balance to hold the flute; under the bottom lip, between the second and third knuckle on the left hand pointer finger and the right hand thumb. (Have a look at my article Flashy Fingers under Articles on this site for a more detailed explanation of this) The job of the right hand thumb is to move the flute in a forward, slightly upwards position producing a gentle counter-resistance against the left hand. Instead, many players place the right hand thumb under the flute and use it to lift the instrument. The problem with doing this is apart from jamming up your fingers (see the afore mentioned article) it causes the flute to roll inwards and hence causes over covering of the embouchure hole. You then end up with all the sound problems discussed in the previous post. So try to remember that your hand positions are not only related to your figure technique but can also have a big impact on your tone quality.