So often in nature we see a strong inclination for objects – or the spaces they contain – to vibrate at certain frequencies.  Musical instruments exploit and maximize these natural tendencies – using air columns, strings and resonating chambers. There are complex regimes of vibration that are easily established for any given length and volume of the bore.

After you’re done with the Rossini keep the bottle.  It’s a great way to demonstrate the natural resonating frequencies for the airspace inside the bottle.  Just as hitting a tuning fork causes the mechanical energy of that impact to set up a specific and long lasting tone, so blowing across the open end of the bottle excites the natural resonating frequency of that particular volume of air.

Imagine if you had gargantuan lips…you might be able to get a pop bottle sound on the bassoon by fingering a low Bb and blowing across the open end of the bell.  In reality, the large diameter of the open bassoon bell discourages this being a useful way of playing the bassoon.  But if you finger that low Bb, and get a friend to slap the palm of their hand at the top of the bell, you can hear the natural resonance, albeit briefly. A simpler way to test the natural resonating frequency is to finger that low Bb, blow into the bocal and slap your tongue against the open bocal tip. [Hut.  Hut. Hut.] This is analogous to playing a violin pizzicato – a quick energy impulse and the recognizable pitch only lasts briefly.  But even those brief inputs will create a recognizable pitch.  Nature wants to sing!

The point is, there are different ways to excite vibrations in the bassoon bore, including the single impact, unidirectional slapping at one end or the other and the imaginary method of playing at the bell end like a pop bottle or flute.   However, just as a violin needs the continual energy input of the bow on the string to sustain a tone, the bassoon needs an efficient interface between resonating bore and the blowing energy of the player.

The hair of the violin bow interacts mechanically with the violin string, microscopically catching and releasing to continually excite the natural frequencies of the string.

In most wind instruments [excluding the flute] the interaction between player and sustained bore resonance is achieved by means of a pressure controlled valve.  I introduced this term in the previous chapter.  You might visualize it this way…

The catch and release process of the bow hair on the string happens at the same frequency as the primary resonance frequencies of the string.  If the violinist is playing a middle C, the rough surface of the bow hair interacts with the string 262 times per second.  That frequency is not determined by the pressure of the bow or speed of the stroke but by the natural frequency for the particular string at that particular length.  You can draw the bow at different speeds and variable force.  Amplitude/Volume changes and Harmonics/Colour vary, but the pitch remains constant.

Similarly, the bassoon reed must convert steady blowing pressure into ‘pressure pulses’ at the frequency of the natural bore resonance of the bassoon for the note you select.  If we finger a middle C, the reed will reinforce pulses of air pressure 262 times per second.  These pulses repeat at this frequency regardless of how loud or bright you might be playing!  Because pressure controlled valves like bassoon reeds and trumpet players’ lips are feedback mechanisms, theirf operational frequency is controlled by what’s happening in the bore.

The bassoon reed is a pressure-controlled valve.

I mentioned water taps above.  These are valves that allow pressurized water from our municipal systems to flow into our homes.  But let me be very clear about how I am using the word ‘pressure’.  Obviously, when you blow into a bassoon the air in your lungs and mouth is under pressure.  Your embouchure is under pressure.  Your psyche is under pressure!!  These are not the same as ‘acoustic pressure’.  Acoustic pressure comes from the bassoon bore.  Think Conga Line.

And it’s worth repeating what I said above while comparing bows to reeds.  Blowing pressure controls loudness, not pitch.  Variable blowing pressure changes the amplitude of the vibrations.  It’s the acoustic pressures – dancing like conga lines – within the bore that control the frequency of those vibrations.

I suppose we could define the bassoon reed as ‘a valve whose frequency of operation is controlled by the changing internal acoustical pressures in the small end of the bore’, but that’s a bit of a mouthful.

I promise to come back to this, but we first need to look at how airflow through a reed initiates vibration.

Chapter 6 – We’ll Huff and We’ll Puff

Chapter 1 – Starting Down The Path  Chapter 2 – It’s A Simple Question? Chapter 3 – Surf’s up! Chapter 4 – The Physicist’s Viewpoint Chapter 5 – The Big Picture Chapter 6 – We’ll huff and we’ll puff… Chapter 7 – Look Both Ways Chapter 8 – Dialogue Chapter 9 – The Big Bounce Chapter 10 – The Incredible Shrinking Bassoonist Chapter 11 – A Useful Equation  Chapter 12 – Goldilocks’ Dilemma Chapter 13 – Stairway to Heaven Chapter 14 – Reed MyLipsChapter 15 – Resonance Chapter 16 – Corvids & Cacks Chapter 17 –   Chickens and Eggs Chapter 18 – Chiaroscuro  Chapter 19 – Donuts​ Chapter 20 – Balance

 Doodles & Design by Nadina

Art by Hermann Armin von Kern