The Kingma System allows for reliable, even-sounding quartertones across the majority of the instrument's range. It is important to note that exact quartertones are not available below d', due to the already demanding role for the right hand little finger (see Range). The quartertones retain the tone quality of standard pitches, and the additional venting that the Kingma System provides allows for smaller intervals, such as eighth tones, to be produced through a series of modified fingerings. Smaller intervals are also possible through alternative fingerings, although these can sometimes be difficult at high speed. Small microtonal pitch increments can also be produced through pitch bends. Due to the complexity of microtonal fingerings, and the size of the instrument's keys, transitions between notes can sometimes be slow, and care is required when writing fast passages.
For accurate intonation of small microtonal intervals (for example, in spectral music where a composer may require a particular frequency of pitch) it can be useful to provide the performer with a recorded reference pitch.
Microtonal fingerings become more difficult to reach and less reliable towards the very top of the instrument’s range. This is due to the general tendency of bass flutes to become sharp in the upper register, combined with a somewhat unstable reponse of higher pitches due to the instrument's size. The fingering modifications used to stabilise the pitch can slow down microtonal movement in the high register.
Agility of quartertones
Standard flute playing involves the player raising and lowering the fingers on prescribed keys (usually one key for each finger). The Kingma System has a more complex mechanism, especially on the bass flute where the keys are spaced a distance apart. The key-on-key system is developed here to incorporate some open holes and some extra keys, resulting in a fingering system which relies on a combination of uncovering the central open holes of the keys, and sliding off two keys onto one with the same finger. Each finger often operates more than one key simultanously. Sliding from an open hole onto the rim of a key, or reaching some of the additional levers on an instrument of this size can require a considerable change in hand position. The result of this is that the movement between pitches has less agility than the alto flute or C flute, and care should be taken when writing complex note patterns at high speed. The fingering system is logical, and based on sharpening standard fingerings to produce the quartertone above.
Microtonal fingerings require a change of hand positions from the standard playing positions. This means that rapid microtonal movement can require considerable physical movement. Ordinarily, note changes require the fingers to move up and down, with no other hand movements. This is obviously considerably quicker than a movement which involves sliding a finger or shifting the whole hand position.
Sliding movement to create quartertones
Chromatic movement in low register
Notation of microtones
As previously mentioned, the fingering system for the Kingma System bass flute relies on sharpening standard pitches in order to create higher microtones. This means that for the purposes of quick reading, quartertone sharps are easier for the player to execute. However, in a piece of music, it is often best to follow theoretical convention with the use of sharps and flats, and to notate them as shown below:
Quartertones may also be indicated using arrows on the accidentals before each note, though it must be made clear that these are in fact quartertones rather than pitch bends. Some composers prefer to use this system for pitch increments of less than a quartertone, so it is advised to make this clear in a glossary.
For smaller pitch increments, precise frequencies may be given (eg +27 cents etc).