the abdomen

The abdomen is far more strong and agile than the chest when it comes to breathing. To develop good breath control, the breathing should be completely abdominal. Regular abdominal crunches will come a long way in developing a powerful as well as a delicate breath.

blow through

Imagine you are not just blowing into the flute, but through it. Imagine you are targeting an object 2 meters away by a steady stream of focused breath.

steady flow

the ability to blow a steady breath is the key to good tone and intonation. This can be achieved only through abdominal breathing.

breath pulse

complimenting a steady flow of air is a pulse of breath, essentially the "ha" whisper. You should be able to produce a short yet powerful pulse of breath, again using the abdominal muscles only (without any lip or tongue articulation).

resistance

Unlike most wind instruments, the flute does not offer any resistance to the air flow. You blow against a resistance coming from within your body, mainly the throat and the lips. Controlling this resistance to air flow is an essential part of regulating the breath. It is bad practice to use the throat in offering or controlling the air resistance. The throat should be open and relaxed, just like when you are yawning. All the resistance (and its variation) should come from the lips.

The formation of the lips and the muscles around them while playing a wind instrument is called the embouchure. In flute playing, the manner in which the lower lip is placed and presses against the flute is also an integral part of the embouchure. The embouchure largely determines the tonal quality and intonation and takes years to develop.

The embouchure is not fixed throughout your playing, but goes through subtle yet innumerable variations across the range of notes, volume and articulations you produce. Even a different flute often requires a slightly different embouchure.

Thus the embouchure is dynamically adjusted according to the situation, sometimes as often as several times in a single second. Developing a good embouchure is not just a matter of arriving at an optimal formation of the mouth muscles, but involves development of sensitivity and versatility of the muscles involved to anticipate and adapt to the situation at lightning speed.

flats

use the flats of the fingers and not the tips to close the finger holes

far edge

It is common for beginners to leave a small gap at the far edge of the finger hole, especially on the third finger (see picture). Usually they aren't even aware of it. This leads to a poor tone or (more often) no tone at all. Very frustrating.

Use a mirror to check if you are doing it too.

It helps to give special attention to the far edge of the finger hole every time you close it. The near edge is seldom left open except deliberately.

near edge

While opening a finger hole, the near edge should be opened first and then the rest of the hole. This results in a smooth transition between notes.

direction of movement

The fingers should move like they do while closing or opening a fist, in and out, never sideways. Side movement can be neither precise nor fast. It may appear easy (in the beginning) to move the fingers sideways, especially for half opening the holes, but that is not a good practice. Partially lifting the finger (near edge first), though counter intuitive, is a much better technique.

it is not just the fingers

opening and closing the finger holes in tune and rhythm is a complex activity and involves not just fingers but hands, arms and shoulders as well. If anything, the role of fingers is relatively passive compared to the motion of arms.

pivot inversion

This is the most counter intuitive part of finger technique. Fingers muscles are rather slow and clumsy when it comes to independent movement. It makes more sense to move the fingers up and down by the movement of the whole arm while keeping those covering holes pivoted at the holes. This is best illustrated through the following animation.

Notice how the whole arm-hand-flute assembly moves up and down to accomplish this efficiently.

Conceptually, articulation in flute playing is not very different than articulation is speech. Consequently, articulations can be easily referred to (or named) by the corresponding speech articulation sounds.

The typical flute embouchure is similar to the one made for speaking the vowel 'u' or 'oo'. Thus it is natural to associate this vowel to flute articulation sounds (or names).

Articulations can be complex and innumerable. But the most commonly used are just a handful.

hu

perhaps the softest articulation. Lacks an edge. Performed completely using the abdominal muscles and no variation in the embouchure.

phu

nothing more than an extension of hu by adding a minute lip movement.

du

most frequently used articulation.

tu

a sharper version of du

dugu

also known as double tonguing, this can get twice as fast as du and is used when a continuous chain of articulations is needed.

tuku

a sharper version of dugu. This is more natural for double tonguing at higher pitches while dugu is appropriate for lower pitches.

rrr

rolling the tongue while maintaining a tone produces an effect almost like the rolling of drums. Quite difficult to manage a good rrr for very high as well as very low pitches.