There are several causes of troubled high notes but first let's define the symptoms.
This post will be the first of several addressing this common issue.
Squeezed or tight high notes.
Feeling like there's a ceiling on the tone.
Intonation: flat and over pressurized.
Pushing one register too high.
Retracting the tongue to create a "false space"rather than widening and lifting the palate above the root of the tongue.
Too much breath pressure. This causes the larynx to be high and the cords can't adduct properly.
SOLUTION: Part I
Sing "ng" on an arpeggiated scale, making sure that the root of the tongue is not pushing down on the larynx, beginning at C4. Notice how the sympathetic vibration behind the nose changes at each register and that vocal weight drops as you ascend. This will give you a "map" of where you will feel your voice resonate . It will also engage the proper breath support and manage the air pressure to air flow ratio.
Notice how the soft palate incrementally widens and lifts in relationship to the "map" you just created. It is crucial that the "ring" of the "ng" be accompanied by the widening/lifting of the palate above the root of the tongue. Think of the palate and the tongue mirroring each other: they both widen and lift (tongue lifts out of the throat and the palate lifts above the tongue). Begin experimenting with opening up the sound by arpeggiating (with good air flow) up to the high note on "ng" (jaw back and relaxed). Release the tongue to an "ah" vowel making sure the tongue doesn't retract into the throat but stays wide and the root high in the mouth. Sigh off the high note in an "organic" fashion using your full voice. Do this as many times as it takes to feel the coordination of the palate and tongue.
In the next post, I will discuss how to achieve stability of the larynx without forcing it down with the root of the tongue.
Questions? Email me at firstname.lastname@example.org