The real singer or instrumentist lets his inner vibration take off from the bottom of his sound column, which he can perfectly visualize from his heels, thanks to his down-flowing relaxation extending his natural inhaling : he should then maintain this tension-free feeling located at his roots level, regardless to the pitch height, thereby ensuring an homogeneous vibration in the whole range of his body radiating sound in space.
We can then talk about the personal tone color.
Because of this activation and the special ability of the skeleton to transmit sounds, the control adopted by the bony voice is direct, conserves energy and maintains the integrity of the full spectrum of sound.
This production has nothing in common with ordinary vocal emission, even if that emission sounds easy. This degree of control is difficult, if not impossible, when we use only air conduction. Bone filters for higher sounds at the expense of lows, making sounds that are particularly rich and dense.
(…) It is easy to see the advantages of an emission that is easily controlled and rich in high frequencies. It has a propensity to align the spine. This in turn facilitates emission, releasing progressively more energy.
If [the sound] is not going to come from the mouth or nose, where will it come from ? You make it with the whole body through the excitation of the spinal column and the contact between the larynx and the cervical vertebrae.
Bone conduction has a special timber, rich, heady and colorful. It has an ethereal quality and seems to come from outside the body. It literally awakens the environment with a smooth, vibrant and dense sonority. It carries with ease.
What is more, when you have it nailed, this sound can be quickly modulated over the entire vocal range without costing you any effort.
Alfred Tomatis, The Ear And The Voice
(translated by Roberta Prada and Pierre Sollier)