PLANIFICACION EMPRESARIAL DEL NUEVO DIARIO

I

They are in a frisky mood as twilight approaches, because it will soon be feeding time. To amuse themselves they are taking turns to play a simple tune—first the violin, then the flute, then the saxophone. Each instrument plays exactly the same notes as the one before but, of course, they all sound different—any listener could tell which instrument is which.

The distinctive sound of each instrument is called its timbre (pronounced “tarmbruh”). If we ask a sax player to play “Three Blind Mice,” and then ask a xylophone player to repeat the tune (using the same notes), it will be obvious that the difference between the timbres of the instruments is enormous, so how can we say that they are playing the

“same” notes?

To answer this question we have to think about what is important as far as our hearing is concerned. The main job of our hearing system is to keep us alive and so the first thing your brain and ear must do when they encounter a sound is to analyze whether or not it is a danger message.

When analyzing a sound for its danger content, our brains concentrate primarily on the timbre of the noise, seeking to work out whether the sound is being made by a small animal (rabbit is on the menu) or a tiger (I am on the menu). Fortunately it doesn’t take long for our finely tuned intellects to work out that we are unlikely to be eaten by a xylophone. The second most important thing to do is to work out which direction the sound is coming from. Once again the brain leaps into action: “That plinking noise is coming from over there—from the general vicinity of that xylophone.”

Having worked out that the situation is musical rather than lethal, the brain concentrates on the frequencies of the notes being produced and their general arrangement into melodies and harmonies. In the context of

music, the timbres of the notes have some importance, but this is secondary to the frequencies (or pitches).

We identify two notes as being similar if their fundamental frequencies are identical, irrespective of any difference in their timbre. The timbre adds extra interest to the situation—in the same way that shading adds information to an outline drawing. This musical shading can have a big impact on the emotional feel of the music, which is why those violinists who walk from table to table in Italian restaurants are unlikely to be replaced by xylophone players.

Although we are going to concentrate on the timbre of individual instruments in this chapter, it is worth remembering that, in many cases, the overall timbre of a piece comes from the combination of instruments involved. When writing a big orchestral piece, the composer spends a lot of time deciding which instrument, or combination of instruments, gets to play which bits of the melody and harmony, in order to present the music in the most effective way. It’s quite a balancing act to combine the various loudnesses and timbres of the individual instruments to produce an overall “voice,” or timbre.

In the case of a four-piece rock band, the distribution of notes is pretty obvious, but the instrumentalists can choose a wide range of timbres for their instruments. The lead guitarist will press various buttons during the course of the song to make the sound more or less aggressive, and the keyboard players can do the same, or move from instrument to instrument. I will describe this button-pressing malarkey in more detail at the end of chapter 5 in the section on synthesizers, but for now, let’s look at the timbres of individual, non-electronic instruments.

Here are three notes of the same frequency with different timbres.

These wave patterns represent the variation in air pressure experienced by an ear. Imagine these wave patterns “washing up” against the eardrum just like different types of waves washing up on a beach.

Recorded wave patterns of three notes with the same frequency but different timbres. Note that in every case there is more than one “hump”

in each complete cycle. (Source: Measured Tones by I. Johnston (Taylor

& Francis, 2002)).

In the case of the top wave pattern, the eardrum will move backward and forward in an even, regular way as the air pressure goes up and down.

This will result in the brain experiencing a rather pure sound. The wave pattern shown here is a trace of a note from a flute—which sounds smooth and even to our ears.

The middle and lower waves in this illustration are also repeating patterns, but in this case the pressure variations felt by the eardrum are more complicated and jerky, causing the brain to experience this sound as richer and less smooth. These notes are the same fundamental frequency as the one played by the flute—and are therefore the same note—but this time they are played on an oboe in one case and a violin in the other.

But why should a flute make a sound which is smoother and less complex than that of a violin or oboe? To answer this question we have to think about musical instruments as machines which produce notes. All these machines are designed to produce repeating ripple patterns of pressure in the air and they all do this in different ways. For example, playing a flute involves a straightforward method of setting up vibrations in a column of air. There are no moving parts inside a flute, just this simple vibrating body of air. Playing a violin, on the other hand, involves

a rather complicated method of vibrating a string by scraping it with a bundle of sticky horse hair (more about this later). The string then passes its rather jerky vibration onto the body of the violin—which is an unusually shaped wooden box. Although the overall vibration of the box will repeat at the fundamental frequency, various parts of the box will vibrate in different directions. So, rather than singing with a single voice (like the flute), a violin is more like a choir of several different voices, all singing the same note. Some of these voices are gruff, some are squeaky and, combined, they give a complicated, rich sound. The relative importance of the various parts of the “choir” changes as we play higher notes, where, for example, the squeakier members might have more influence, so the timbre of a violin differs quite a lot over its range. A skilled player can even play a single note with different timbres. If you play with your bow near the center of the string, you encourage the mellow part of your choir to contribute more to the note. If, on the other hand, you use the bow near the end of the string, close to the bridge, you will get a much harsher, more aggressive sound. On instruments which sing with far fewer “choir members”—like the flute—the range of timbres is much more limited, but even in these cases the timbre is different between high and low notes.

So, if instruments don’t have a steady, identifiable wave pattern over their whole range, how do we recognize them so easily no matter what notes they are playing? Well, we make our decision about what type of instrument it is from two main sources of information:

1. The sound the instrument makes when the note is just starting;

2. The sound the instrument makes while the note is playing.

Let’s look at these two things separately.

Differences between instruments when the note is just