What Is Pitch?
The relative height of a sound, ranging from high to low.
Here are a few different pitches. Each of these are at a different height.
The three pitches in the soundfile above might be described respectively as Low, Medium and High.
Beyond Traditional Ideas of Pitch
In traditional musical notation, pitch is indicated along the vertical axis of the stave. The pitches of sounds can be quickly described as being low, medium or high. However, we can split this into as many registers as are required (e.g. Low-Medium, High-Medium, etc.).
This is a pitched sound. A sine tone is the most simple pitched sound.You can see the simplicity and the focus of this sound energy by looking at a spectrogram of the sound.
A noisy sound which has no clear pitch.
Some sound sources produce more than one pitch.
This single horn sound contains multiple pitches playing at the same time.
This is a spectrogram of a triangle wave. A single triangle wave is itself made up of many individual pitches, we see them here as stripes.
What Causes Pitch?
Pitched sounds are caused by regular vibrations. If an object vibrates in a regular way (moving back and forth smoothly), then it will create a pitched sound. The less regular the sound vibrates, then the noisier it is. We can experience this by rubbing our finger around the damp rim of a glass to make it sing.
- Ask someone at home if you can borrow a wine glass (or any glass with a stem).
- Pick a glass that makes a good ring when you tap it.
- Wet your finger and the rim of the glass.
Then, while holding the glass firmly with your non-writing hand, take the first finger of your writing hand and rub it smoothly and steadily around the rim of the glass.
- If you are able to make smooth and steady regular motions around the rim, the glass should begin to sing, creating a pitched note.
- If you move your writing hand in an irregular way around the glass, then no pitch will be created.
Why is Pitch Created?
The smooth and steady motion of the hand around the rim of the glass causes the glass to vibrate in a regular way, and thus produces a pitched sound.
By changing the level of liquid in the glass, it is possible to change the pitch. This is because the liquid dampens the vibrations where it touches the glass, thus changing the amount of the glass which is free to vibrate.
The more liquid in the glass, the smaller the surface that can vibrate and the higher the pitch produced.This process is similar to the way in which changing the length of a string on a guitar or violin will change the pitch made (shorter string = higher pitch).
Changing the Pitch
Using technology, it is possible for us to change the pitch of sounds. The process is known as pitch-shifting or transposition. This technique is often used in pop music or cartoons to create high pitched voices.
This is the original unedited recording.
This is the pitch-shifted version in which the sound has been increased in pitch. This can be a really useful effect to transform and develop sounds. See: Transformation, for an example of pitch-shifting in creating transformations.
Try to use a mixture of high, medium and low pitched sounds in your compositions.Using a range of different pitches allows you to fill up the whole sound range and provide a much richer soundscape.
Changing Pitch Over Time
The amount of pitch-shift increases over time.
Listen out for pitched sounds around you. How would you describe their pitch?
- Are they high/low?
- Are they changing/constant?
- Are there multiple pitches?