Buccal control is the essential counterpart to diaphragm control. Diaphragm control focuses on providing the raw air-stream for the tone, while buccal control is used to shape the timbre of the tone, i.e. to incorporate various oscillatory components into the air-stream before it drives the air column within the dizi.
Here, we make the distinction of external versus internal buccal control. The external buccal control consists of controlling the embouchure and the jaw position which affects the velocity of the air-stream leaving the dizi player, while the internal buccal control deals with the tongue position and the buccal cavity shape, which affects the resultant harmonics that are present in the same air-stream.
Naturally, we will consider the external buccal control first, followed by the internal one.
External Buccal Control
We begin with talking about the external buccal control mostly because they are the most easy to observe since any changes can be seen either through a third party or through a mirror. We will look at this from the perspective of the embouchure, the embouchure position relative to the embouchure hole (or chuikong), and the jaw position.
The final control for the driving air-stream of the dizi lies in the control of the embouchure. Technically, the embouchure describes the shape the lips make when performing both the final compression to raise the length of the jet-stream and the directing of the angle in which the jet-stream oscillates through the embouchure hole or chuikong.
The embouchure shape is a generally symmetric aperture formed when the four orbicularis oris muscles maintain nearly equal amounts of pressure against each other. Traditionally, a purely symmetric embouchure shape is required for aesthetic reasons, but the trend these days is to allow up to some amounts of skew in the embouchure shape due to innate asymmetry in the orbicularis oris muscles, particularly when the upper lip has a dip near/at the centre of it.
The embouchure angle as made by the lips is informally described as being ``parrot-shaped'', i.e. the lower lips are ``tucked in'' compared to the upper-lips. The jaw position plays a much larger role in controlling the angle than the orbicularis oris muscles.
Traditionally, the rule of thumb is that the lower the pitch of the tone desired, the larger the aperture, and the more relaxed the embouchure (i.e. orbicularis oris muscles) is. For the normal range of dizi played, this rule of thumb works well, but in the extremes (like the xiaodi or the dadi), this rule of thumb breaks down, ending up with too much lipping.
The real governing factor for pitch is the length of the effective jet-stream, with a shorter one for a lower pitched tone, and a longer one for a higher pitched one, while maintaining as compact an embouchure hole as possible. This leads to a more consistent playing that makes leaps responsive, and enables low tones to not sound diffused. But this is not the full story on pitch control---we will talk more in jaw position.
The best embouchure shape and angle is often determined by the shape and cut of the corresponding embouchure hole of the dizi (the 吹孔 or chuikong). The shorter the blowing edge, the more compact the air stream width is and thus the tighter the embouchure required. The larger the angle of the undercut (relative to the normal of the blowing edge), the more shallow the angle of the embouchure (relative to the horizontal). Most dizi have elliptical chuikong and a slight (less than 10°) undercut, and thus once an embouchure shape and angle is learnt on one dizi, it tends to hold for others as well with minor changes.
For a beginner who has never played any flute-like instrument before, getting the right embouchure shape just to get a tone out of the dizi is often the hardest step.
Embouchure position deals with positioning of a dizi player's embouchure relative to the embouchure hole. The principle is to allow the lower lips to cover between one quarter to one third of the embouchure hole, with the aperture centred over the minor axis of the embouchure hole.
A quick way to get close to the right position is to first start with using the centre of the upper lip to ``feel'' the embouchure hole before rolling the dizi outwards and downwards along the lower lips until the embouchure hole is parallel with the horizontal plane.
The embouchure hole being parallel with the horizontal plane is important because it provides the ``best'' neutral position from which the tone can be shaped by varying the other variables without sacrificing pitch frequency correctness.
If the dizi is more ``turned in'' (i.e. the embouchure hole is more obscured by the lower lip), the flatter the tone, while the converse of being more ``turned out'' (i.e. the embouchure hole is more uncovered by the lower lip), the sharper the tone is.
For a beginner who has never played any flute-like instrument before, this is the second hardest thing to get right. It acts as a confounding variable to the neophyte as the embouchure shape is being figured out.
Jaw position is often overlooked when it comes to buccal control, mostly because it is often used for fine-tuning, with the reliance on the effective jet-stream length as the primary means of determining pitch. In most instances, playing at a moderate dynamics level will not require much manipulation of the jaw position, but when the very soft or the very loud dynamics are needed, jaw position is important to maintain the correct intonation.
The most effective way to change the angle of the embouchure is to start with the jaw loose and opened for the low pitched tones, and to slowly close it as the pitch jumps between the harmonics of the dizi.
The key principle behind jaw movement is to use the rigidity of the teeth to support and shift the lower lips either forward or backward to adjust the angle. Naturally, this ends up with subtle movements of the dizi forward and backward of no more than 3mm, enough to change the embouchure angle substantially.
Beginning and intermediate players may use the jaw positioning mechanism to ``lip'' the notes---it may work for a while, but it is less responsive for fast passages when compared to proper jet-stream length control via breathing. Jaw position control should always be used to perform fine-tuning when changing dynamics as opposed to correcting intonation issues at moderate dynamics from improper technique.
As to how much of the jaw to open to for the lower pitched tones, the buccal cavity will give a few pointers on how to do so.
Internal Buccal Control
The internal buccal control concerns everything behind the lips and inside the mouth. The two main components here are the buccal cavity and the tongue position.
If explaining the tongue position precisely is equivalent to defining consonants, then explaining the buccal cavity precisely is equivalent to using the relevant vowels.
As a general rule of thumb, the buccal cavity (the kouqiang (口腔)) should be kept as relaxed and enlarged as possible, as though one were taking a [closed mouth] yawn or making the ``ha'' [hɑː] sound. This ``ha'' technique (``ha'' qichuifa (``哈''气吹法)) brings out the lower harmonics of a tone more strongly. Combined with the deep breathing technique, this provides the most voluptuous tone that one can get out of the dizi.
The ``ha'' technique works well for the dizi due to the mechanism of the dimo---if playing on a dizi with either no mokong or if the dimo is replaced with something very tight, this method tends to create a very muddy sound. The proper corrective action here to learn the proper buccal cavity tuning by ``listening'' to the vowel sound present in the dizi through the embouchure hole.
To ``listen'' to the present vowel sound, cover all the tone holes with the fingers, and place the embouchure hole near to one's ear. The constrained echo within the dizi will yield something that sounds like a vowel---mimic that vowel with the buccal cavity and that will be the proper shape of the buccal cavity.
Tongue Position (at rest)
There are two main categories for tongue position: at rest, and in motion. At rest refers to the sustain portions of a tone where a long tone (i.e. in legato) is expected, while in motion refers to how to control the tongue in more heavily articulated scenarios.
For the purposes of buccal control, we will only consider the category of tongue position at rest, and defer the in motion discussion to the article on tongue techniques.
While the traditional explanation uses onomatopoeia to describe tongue positions, we will make use of the International Phonetic Alphabet to explain the positioning more precisely.
While the ``ha'' technique increases the overall volume in the buccal cavity, it is insufficient to produce the correct tone since that same volume is incorrect for all the harmonics that the dizi can handle. As such, a more precise notion of where the tongue should be at rest can be constructed like the table below.
|Excited dizi Harmonics||Buccal shape|
From the previous table, we observe that with high notes, the tongue assumes a more closed and forward position without completely obstructing the air-stream to become a consonant, and as the harmonic to excite lowers to the fundamental, the vowel steadily gets more open and moves farther back on the tongue. Taking these positions into account is the start towards having a wonderful tone, and can build up towards good tonguing techniques.
The change in vowel sounds for the different harmonics of the dizi is also why there are many variants on the mnemonic for double tonguing in the literature---each of them refer to a different energy standing wave within the dizi itself.