Ever wonder why someone's voice sounds so much different on the phone than in person? Well, the digital signal has slightly altered the sound of their voice, just enough so that it sounds strange.
The way something sounds and our ability to recognize what we're hearing has to do with something called timbre (TAM-bur). Simply put, timbre is how something sounds. It's the difference between the crackle of fireworks and a sweet melody played on a violin. Differences in timbres allow us to instantly recognize a sound. If you hear a car alarm go off, you know it's a car alarm and not a police siren because it has a particular sound quality that you're familiar with. Musicians also call this "tone color" but I like to think of it as "tone shape". Another great example is when you hear the sound of your mother or a close friend calling your name - it's unmistakeable; you know it's them because you're so "tuned in" to the particular sound characteristics of that person's voice.
Now let's get to music, where we can really have fun with timbre. Again, I like the idea of thinking of sound as a shape because sound engineers and scientists have learned how to "see" sound. They use an oscilloscope to view the shape of a sound wave.
Let's back up. Sound is understood as changes in air pressure which occur in waves. We can measure a sound wave's amplitude (volume), frequency (pitch) and also talk about its shape using an oscilloscope. An oscilloscope has a small TV monitor that reacts to the incoming signal in such a way as to create an image of the wave.
There are several common wave forms (wave shapes) including: sine, sawtooth, square, and an infinite number of combination of these and others. Electronic music uses these wave forms to create a wide variety of sounds. Sounds from acoustic instruments like a guitar or a clarinet, for example, can be analyzed using an oscilloscope, or computer software.
Here's a simple sine wave:
And here's what it sounds like:
Here's a sound wave from a clarinet:
And here's that sound file:
Listen to the difference in tone quality. And notice how the clarinet waveform is much more complex. The distinctive sound of the clarinet comes partly from the complexity of its wave form (which has to do with how a clarinet is constructed). This is one reason it's difficult to replicate a clarinet's timbre using electronic sound, although software and audio engineers are getting better at this. Frequency (pitch or cycles per second) is an important factor in determining the characteristics of a sound. There are several different frequencies happening in the sound of a clarinet note. There's the fundamental frequency (the pitch or note) that the clarinet is playing, say B-flat, and then there are smaller frequencies called harmonics. These harmonics help to give the clarinet its distinctive sound. They are not as clearly audible as the fundamental frequency but they're very important to the overall timbre.
Now, complex doesn't necessarily mean pleasing, but the subtleties of a bowed violin string or the breathiness of an oboe are part of what give acoustic instruments their sonic 'fingerprint' and remind us that we are listening to the real thing.
Percussion is a great place to really understand the importance of different timbres in music. Let's take the drum set, which we find in all kinds of music including rock, pop, jazz and hip-hop. The three most important elements in the drum set are: 1.) the Hi Hat cymbals (we'll use the abbreviation "HH"); 2.) the snare drum (SN); and 3.) the bass drum (BD). Each of these three elements: HH, SN, BD produce three very distinct timbres.
The Hi Hat is really two small cymbals that are sandwiched together using a foot pedal but are played with drum sticks. The Hi Hat has a bright shimmery sound when played loosely and a short, crisp sound when played tightly. The frequency of the Hi Hats tend to be very high with a loud attack (attack refers to the first millisecond of sound you hear when you strike the cymbal; this is followed by the sustain and decay, which is the part of the sound that dies away). Photo and sound sample:
The snare drum is a drum with a wire snare on the bottom that rattles when the drum head is struck. It has a medium tone quality while the wire snare gives it a buzzing sound which includes higher frequencies; you might describe the snare drum as having a short, punchy sound, with some depth. The sound sample below includes snare drum accompanied by a bass drum:
Lastly, the bass drum is low and booming. It is larger than the other drums and is played using a foot pedal-controlled mallet. The sound has lower frequencies with a softer attack; it has a strong, deep sound. It is used to keep the beat and often falls on the downbeat - see my bog entry "feeling the rhythm: on/off the beat". Photos and sound samples from Wikipedia:
There are lots of example of these three drum elements in action. The Hi Hat usually plays more notes, like eighth notes. Here are some Hi Hat notes written out:
The bass drum hits on the downbeat providing a strong foundation. Here are some Bass Drum notes:
Meanwhile, the Snare Drum strikes on the off-beats (see "feeling the rhythm: on/off the beat" for a basic explanation of rhythm). Here are some Snare Drum notes:
These three timbres, high and light (HH), middle and punchy (SN), and low and booming (BD) work together to create a danceable beat. Here's all three written out together:
And here's what that beat sounds like (computer-generated):
For a "real world" example, here's a beautiful old drum beat from a rap classic. Listen and try to pick out each drum element (HH, SN, BD):
Now imagine if instead of HH, SN and BD there was only BD playing that beat - how dull it would sound! Our ears like to hear a variety of timbres to keep things interesting and keep us coming back for more. Good DJ's and music producers know how to use different timbres effectively to make a great sounding song, one that keeps us listening. They have to think about the type of guitars, when to bring in the drum beat, when to have only strings playing and so on..
Next time you're enjoying a great song, try to pick out the different timbres you hear, from high and shimmery to low and booming..