For a player to be able to sound a musical instrument, there must be a means of inputting energy to set up the vibration. This energy may be introduced in a short, sharp burst or continuously over a period of time.
In the case of brass instruments such as the trumpet and trombone, and woodwind instruments such as the flute and oboe, the player feeds in energy by blowing air into the instrument. The energy can be supplied in a short burst – in which case short-lived ‘staccato’ notes are produced. Or it can be supplied continuously for as long as the player keeps blowing – in which case longer-lasting notes are produced.
With many percussion instruments, drums and triangles for example, the player provides the energy to initiate a vibration by striking the instrument with a stick or similar device. In this case, the energy is supplied in a short, sharp burst.
Stringed instruments such as the violin or cello can be excited in different ways. The player can either pluck the string, when energy is supplied in a short burst. Or they can bow the string, in which case energy is supplied either in a short burst (if the player wishes to produce staccato notes) or continuously (if the player wishes to produce longer-lasting notes).
If a player feeds energy into an instrument in a short burst, the resultant vibration will die away. As a result, the sound produced will be short-lived or transient. If, instead, the energy input from the player is continuous, the resultant vibration will be maintained. The sound produced will be long-lived or sustained.
Listen to the five sound clips of instruments provided in the track below. For each sound, judge whether the energy was introduced in a short burst or continuously, and whether the sound is transient or sustained.
Click 'Play' to listen to Audio Clip 2
The first sound is that of a trumpet blowing a staccato note. Energy is introduced in a short burst. The sound is transient.
The second sound is that of a trumpet blowing a long-lasting note. Energy is introduced continuously. The sound is sustained.
The third sound is a violin bowing a long-lasting note. Energy is introduced continuously. The sound is sustained.
The fourth sound is that of a violin being plucked. Energy is introduced in a short burst. The sound is transient.
The last sound is a snare drum being hit. Energy is introduced in a short burst. The sound is transient.
Identify possible excitation mechanisms for the following instruments and in each case indicate whether the energy is introduced in a short burst or continuously:
The guitar is excited by the player plucking the strings. Energy is introduced in short bursts.
The trombone is excited by blowing air into the instrument. Energy can be introduced in a short burst or continuously.
The piano is excited by hammers striking the strings. Energy is introduced in short bursts.
The oboe is excited by blowing air into the instrument. Energy can be introduced in a short burst or continuously.
The xylophone is excited by striking the wooden bars. Energy is introduced in short bursts.
So what actually happens when a bow is dragged across a violin string, or when a hammer strikes a piano string, or when air is blown through a reed into an oboe? How do these actions supply energy to the instrument to excite a vibration? There are some common principles on which these different classes of instruments rely, and it is these that I want to introduce you to in the rest of this unit.