How to bend notes on the diatonic harmonica: What is “Bending Energy”?
Warning: This blog post contains physics.
Here is an excellent demonstration of what happens when we bend notes. See what happens at the 3:00 minute mark.
When he finds the volume of the tube that is resonant to the frequency of the tuning fork, the sound increases. The frequency of the tuning fork stays constant though. Harmonica reeds are special because they can vibrate at different frequencies. We can make them vibrate faster or slower.
We apply “bending energy” by changing the size of the oral cavity just like professor Sumner Miller changed the size of the resonance chamber (cardboard tubes). Resonance is what applies kinetic energy to the reeds to make them vibrate at the desired frequency. If you want the reeds to vibrate slower, you open up your oral cavity to lower the resonance frequency. The reeds follow. It’s as simple as that.
Hopefully an understanding of what happens as you play a bent note can help you learn how to execute the technique.
Knowing the physics behind it allows you to free yourself from overthinking things. Don’t worry too much about tongue position, “U”-shape, “W”-shape, “G”-spot.... Just make an air pocket in your mouth and when you find the right size, the note will bend. Figure out what works for you to be able to re-create an air pocket of exactly the correct size every time you want to play that note.
It’s a little bit of a moving target when you consider that as you inhale, the tissues of your oral cavity will suck in and the air pocket will shrink. Conversely, the air pocket will grow when you blow bend because of the positive pressure. But with a little practice, your mouth will figure out how to keep the size of the air pocket constant despite these opposing forces.
Your ears play a big role in this. But the interaction between your voice, your ears and the shape of your oral cavity is automatic (or “autonomic”) so no instructions are required - other than to mention to make sure you can hear yourself play!
Overbends are just like regular bends!
Overbends are a little more complicated because we need both reeds (blow and draw) in the system to respond to the same resonance in different ways. One reed needs to stop moving while the other one needs to vibrate at the correct pitch. The trick is to get the reed that is standing still to stay still even though we are applying airflow to the system.
Sometimes out-of-the-box harps are set up to allow this to happen. Sometimes, they are set up to inhibit this. It’s the luck of the draw. It’s a common misconception than you need to practice overbends for years before you can become good enough to play them. The truth is that overbends require breath control, resonance control and a harp that is set up to cooperate.
It’s likely that you can learn to use overbends musically in a matter of weeks with the proper harp and some dedicated practice. You don’t need to build muscle over several years like a bodybuilder. You simply need to learn fine motor control.
I really enjoy watching professor Sumner Miller. Here is another video from the good professor where he describes the phenomenon of beating. Again, watch starting at the 3:00 minute mark:
Hearing the beating is a very important part of how to tune a harmonica.