HALF-HOLING
The following is from "The Double Reed Connection" Issue No. 6, Spring 1995. An Essay from Professor Darryl Durran
There are two issues that must be addressed to achieve proper half-hole mechanics: basic left-hand position and movement of the left-hand index finger
Left Hand Position - Getting this right is more than half the battle.
Hold your left hand as if you are playing the violing with your fingers curved over the fingerboard. Visualize the violin's neck laying on the inside of your palm. Note that the fingers form an angle of less than 90 degrees with the visualized violin neck.
Place your right arm across the front of your body so your finger tips are on the front of your left shoulder. Place your left hand in its "violin position" against the bottom of the right forearm just above the wrist. Support the weight of the arm with your left hand. The base of the left-hand index finger, at a point opposite the thumb, should be at the part of the hand that is supporting the weight of the arm. Note that the fingers form an acute angle in relation to the wrist and hand. The position of the hand against the arm is very similar to the position on the bassoon.
Transfer this position to the bassoon, maintaining the angle between the bassoon and the hand while covering the left-hand holes and pressing the whisper key with the thumb. The index and middle fingers will probably be fairly arched while the ring finger is fairly flat. Avoid any double jointing of the fingers. Double jointing is an indication that the player is squeezing the bassoon between their thumb and fingers and not allowing the bassoon to rest at the base of the index finger.
Right Hand Position
With your left hand in the correct position, try rolling the first tone hole open while retatin the feeling of the above exercises. Be sure that the index finger is rolling not sliding on the instrument. Also be sure that the index finger, NOT the wrist, is moving to open the half-hole. When half-holing, the bassoon should be seated against the base of the index finger. The bassoon should never be held with just the ends of the fingers. When half-holding be sure that the index finger retains its arch and the base of the finger is in contact with the bassoon
With the left hand in the proper position you will sense that when the hold is closed the index finger is leaned into the bassoon. The tone hole should make contact with the finger a little off center, on the side of the finger that is away from the heel of the hand. When you roll the hole open think of the movement as rolling to a neutral position. USE A MIRROR TO OBSERVE THE HALF-HOLE MOVEMENT.
Advanced Half-Hole Technique
Now the subtleties. While this technique is called "half-holing", the amount of hole actually opened should be about 2/3 for F# and G, 1/4 forG#. If not enough hole is open for F# and F, the note will crack or sound choked. For G#, too much hole open may cause response problems. Be sure the whisper key is closed for all three of these notes. When F#, G or G# is approached from fourth-line F (when the hole is not covered), the index finger must be placed down in the rolled-open position. Half-hole is used for F#, G and G# an octave higher as well.