Overblowing is a characteristic of the contraforte and simple to execute. This effect is executed in the bottom register of the instrument. I have recorded an octave of overblowing from the fundamental where I gradually increase the harmonic layering by tightening my embouchure and moving my lips to the back of the reed then I do the reverse to decrease the harmonic layering.
I have recorded examples of WEAK HARMONICS that should NEVER BE USED as the harmonic laying is simply not there. These are executed on the notes F2 to A2.
I do not consider the result of the technique of overblowing to me as a contraforte player is not a multiphonic, it is a physical technique which brings about harmonic layering.
Overblowing a bottom F results in a WEAK effect.
Overblowing a bottom F# results in a WEAK effect.
Overblowing a bottom G results in a WEAK effect.
Overblowing a bottom G# results in a WEAK effect.
Overblowing a bottom A2 results in a WEAK effect.
I discovered that I could isolate harmonics on the contraforte and trill these fingerings when overblowing, which resulted in a very different building up of sound. The audio examples below starting from bottom A to bottom E demonstrate this:
Then I opened the ocatve keys—1, 2 and 3—when play F–A and discovered this:
An explanation and more examples of overblowing are provided in the video below:
Contemporary Contraforte 