Pitch bending technology for free reed musical instruments


How does it work?

There are two main mechanisms involved in acoustic pitch bending technology for free reed instruments: 1) one by which the reed can be made to alter pitch, and 2) one by which the musician can be made to execute the bend. 

There are many possible mechanisms in the first category, though not all can be incorporated practically into a real instrument.  Here, we group these methods into three categories:  a) methods that do not make direct contact to the reed tongue, b) methods that directly contact the reed tongue, and c) methods that incorporate the use of an additional vibrating body; e.g., another reed.  Although (c) is a special case of (a), it deserves separate treatment because of it's additional complexity.  Currently, our prototypes explore option (a), and details concerning this method appear in the next section.    

In the second category - implementing the bend, there are again many ways to choose from, and for simplicity, these can be grouped into a) methods that make use of the keyboard proper, and b) all other methods.  All our prototypes currently make us of (a), with more detail below. 

As digression, we mention certain Asian musical instruments that have free reeds as sound source.  Variations of these instruments, called sheng (China), sho (Japan), and khaen (Thailand and Laos), are classified as free reed instruments, despite the fact that these reeds operate fundamentally differently than their western counterparts. 

For distinction, we might call the Asian free reeds symmetric and the western free reeds asymmetric.  In the symmetric design, the quiescent reed tongue (the part that vibrates) lies symmetrically within its slot.  In the asymmetric design, the quiescent reed tongue lies just outside one side of its slot.  The distinguishing features between these types of reeds rely more upon the use of additional apparatus, and less upon their construction.  The symmetric design is used in conjunction with a resonator (pipe), whereas the asymmetric design is not.  With a resonator, the tongue of the symmetric free reed can be made to vibrate with air pushed through the slot from either direction.  Without a resonator, the asymmetric design can operate only when air is pushed through the slot from only one side - from the side where the quiescent reed sits.   In harmonica playing, with the technique of "over-blowing," the reed is made to resonate with an additional reed, and with the reed tongue vibrating in an "opening" position on the back side of the reed plate.  With the Asian reed, the resonator is especially necessary in order that the musical tone be heard at sufficient volume, whereas the Western reed is loud enough to be heard without a resonator. 

I went through the long winded digression above simply because the Asian musicians and their free reed instruments have been bending notes for centuries, and this activity results primarily because of the presence of an air-column resonator, whose length is determined by the use of finger holes intimately controlled by the player, much like with the clarinet.   On the other hand, the use of selector keys in western instruments and the fact that the western reed does not require the use of a resonator has led western instrument makers away from the concept of pitch bending.  

Charles Wheatstone, an Englishman who invented and developed the English concertina in the latter half of the nineteenth century, was aware of some ways to alter the pitch and volume of bellows driven free reed instruments, but apparently was unable to commercialize them.  Wheatstone did patent some pitch altering features in the symphonium, primarily for tuning purposes, and attempted to develop a large, console type free reed instrument that operated from a wind chest with bendable speaking notes.  The formidable nature of the mechanical design in this latter instrument was apparently not suited for commercialization in either large or small instruments. 

Some western builders since Wheatstone have made other attempts at pitch bending; however, none of these appear to reflect a fundamental understanding of how bending occurs.  We are now into the 21 Century, or 180 years after the first keyed free reed instruments, and finally we have a practical technology that addresses the issue from a fundamental point of view. 

Our presently preferred method for pitch bending is a non-contact method, which acoustically couples the reed to an air chamber that presents an impedance mismatch to the reed.  The enclosed air in the chamber vibrates with a certain amount of  "disagreement" to the vibration of the reed; a compromise is reached between the reed and the chamber, resulting in a change in pitch of the musical tone. 

An analogy to this operation is the following.  Take an automobile with standard shift.  Normally, you start the car from rest with first gear, reach a certain speed, then shift to second, etc., all the way to high gear.  If instead, you try to start the car from rest with the highest gear, there would be considerable "disagreement" between what the engine wants to do and what the dynamics the moving automobile requires.  While you engaged the clutch, the high gear would require the automobile to accelerate extremely fast, in order to keep up with the engine's rpm, but the engine doesn't have enough oomph (torque) to do that.  The lower gears are thus a way to avoid this argument and match the differing characteristics of the engine to the automobile's acceleration.  The same principle applies to the pitch bending free reed, with acoustic coupling replacing the clutch and impedance matching replacing the gears.  In fact, with a large mismatch and strong acoustic coupling, it's possible to not only bend pitch, but also to completely stop the reed from vibrating.  The resulting silence is analogous to popping the clutch in high gear - the engine stalls.  The trick is to provide just the right amount of coupling to the right amount of mismatch so that the pitch is altered as desired.  With our keyboard method of pitch control engagement, the musician is now in the driver's seat, so to speak. 

Concerning direct contact methods to alter pitch and tone of a vibrating free reed, there are also several to choose from.  Our patent disclosures discuss a few of these, and we refer interested visitors to those documents. 

Apart from the basic ideas behind tone altering technology, there are of course many other issues to deal with in building a practical instrument, and the next section addresses some of these.

This web page is a work in progress, and we hope to develop its contents in a way that will reflect the interest of you visitors.  If you have any comments or questions, please mail us

Bend Format

In building prototypes, some difficult questions that need to be addressed early on are: Should the bending tone increase or decrease in pitch?, What is the maximum amount the pitch should change?, What kind of key motion (in the keyboard) should be designed for pitch bending?, etc. 

For the prototypes described on this web site, the pitch is made to bend one half tone (semi-tone) downward.  As mentioned above, the key that selects the tone is used to engage the bend.  When the key is first pressed, with normal force, the normal sound of the tone is heard - with no bending at all.  When an increased force is applied to the key, the key moves further and the note begins to bend.  With maximum force, the key is fully depressed, and the pitch is altered the maximum amount.  There's thus an infinite gradation of bend, from zero to maximum, and all this accompanies a progressively increasing key force.  The response time is essentially instantaneous: as fast as the musician can move the key, the bend will respond. We are considering other bend formats.  For instance, there may be advantages in some kinds of music, or with some kinds of keyboards, in allowing whole tone bends.  And of course, an increasing pitch bend might also have advantages. 

One might look to other musical instruments as examples of bend formats.  For instance, the guitar normally bends notes upwards (by an increase in string tension), beating reed instruments (clarinet, saxophone) can bend in either direction, with extremely large excursions, and similarly for lip instruments (trumpet, trombone).  Most harmonica bending is done in half tones downward, with some downward whole tone bending, and half tone up bends (and sometimes further) for the more proficient players, using over-blowing and over-drawing. 

There's thus a great variety in bend formats among musical instruments, and each can be effectively exploited; the musician takes what the instrument offers and plays.  Our initial choices for bend format have thus been largely influenced by simplicity, robustness, reliability, cost, manufacturability, and other things not directly related to music, thereby defining a hopefully marketable instrument.  As we learn more about the technology and what musicians would like, we can make improvements. 

In summary, and for the present, we are exploring half-tone downward bends, with the latter part of a progressive downward motion of the key devoted to the bend. 

What does the musician do?
What does the musician do?

Probably the best answer to this question is, the musician does whatever the musician can and wants to do.  Pressure on the key can be slow, or the key can be punched.  The note can be, for lack of a better word, "wiggled."  True vibrato can now be played on western keyed free reed instruments!  Single notes can be bent.  Likewise double notes, and verily, whole chords, in unison, or with only selected keys (e.g., only the top key) actually bending pitch.  Adept players can learn to control both bellows and key in such a way that the note starts in the bent position, moving upward to the normal tone, thus allowing up-bends, like a guitar.  For the first time now, a note can be played in two ways: the normal way, and the bent way.  The pitch is the same, although the timbre differs, and this difference adds color to repeated note passages.  

The fact that the technology is entirely acoustic offers special advantage.  For example, the sound of a popped bend, made by punching the key quickly, is qualitatively different from a slow, "painful" bend.   The complexity behind such dynamics would be virtually impossible to duplicate by electronic means, and the effect goes far beyond the "pitch bend wheel" offered by electronic (midi) keyboards. 

Musicians who play a pitch bending accordion in these early stages of product development, with little groundwork laid by other musicians, have a clear field of invention ahead of them.  In mastering pitch bending techniques on his BluesBox prototype, Kenny Kotwitz is able to discover many interesting ways to make sounds that he had never heard before. 

The capabilities of free reed pitch bending technology will be determined largely by the musicians who master it and claim it as there own.  There's much room for individual style here, as in any musical technology, and what pleases some may disturb others.  Some may want to appease, others may want to agitate.  The shackles are off, BluesBox technology is hereby unleashed upon the world! 

Is this a serious technology?
Is this a serious technology?

We believe so.  We already know that the technology is capable of controversy, and controversy suggests seriousness.  For instance, Cajun music has its own distinctive and richly adorned features, and the single row diatonic, along with the fiddle, has achieved a central position in this folk genre.  The fiddle has a wide range of freedom in its excursions from the melody line, especially during breaks.  The accordion on the other hand, has assumed a more limited role with regard to melody line during breaks.  I believe this is partly because the accordion provides a percussive sound in complement to the lyrical sound of the fiddle, but more importantly, also because the instrument is melodically limited, without the ability to play sharps and flats.  Here we have a strong traditional bond, between the capabilities of an instrument and its musical genre, and deviations are taken very seriously.  It's thus  a serious challenge to successfully incorporate pitch bending into accordion Cajun music.  Many Cajun musicians would not care to even try, and some would be vehemently opposed to it.  An obvious conclusion here is that adding pitch bend to an accordion is a drastic modification to the conventional design.  The invention is thus anything but trivial.  Whether a Cajun accordion player who bends notes will someday be accepted within the Cajun community remains to be seen.  Such a musician would perhaps need to be young (at least in spirit), rebellious, and very good.  Whatever the case, such a controversy on the acceptance of pitch bending doesn't exist in some other musical genres, and in these genres, the primary concerns of the musicians involve simply mastering the enhanced instrument itself.   Depending upon their musical genres and types of keyboards, some musicians will find mastering the technology a challenge, while others will find it a breeze.  All should find it exciting and fun.