Music Final

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The phenomenon by which a vibration propels itself through the air. If something is vibrating near you, as it moves toward you it sends out a compression wave (greater than anormal atmospheric pressure), and as it moves away from you it sendsout a rarefaction wave (less than normal atmospheric pressure). Your ear drum will move in when the compression reaches you, and the rarefaction pulls your ear drum outward. So if something is vibration back and forth 440 times per second, your ear drum will also be vibrating at the same rate and you will "hear" or perceive the note "A" around the middle of the piano's range. One cycle, wave-length or vibration will consist of both the compression and rarefaction parts of this phenomenon.

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Rarefaction and Compression

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Amplitude (the phenomenon of sound which is also called "volume" or "loudness" corresponds to the amount of change in air pressure. If the string of a guitar is plucked lightly, the string moves back and forth only a little and creates only a little bit of compression and rarefaction. Therefore, your ear drum only moves back and forth a little bit and you then perceive a 'soft' or 'quiet' note. The note has very little 'loudness,' because the "amplitude" or "volume" of the displacement of the air molecules is also very little. If you were to pluck that same guitar string very hard (by pulling the string back a lot further before letting it go to vibrate back and forth), that string would be displacing more air molecules, thereby squeezing the air molecules together even tighter during the 'compression' part of the wave, and creating even more of a vacuum during the 'rarefaction' part of the wave

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Amplitude/loudness/dynamics

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the speed of the music

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Periodicity/frequency/ pitch

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Transverse waves: These are waves (like light waves or waves on the ocean) that must move in two dimensions: forward or backward AND up and down. I demonstrated this in class by "snapping" a wave through a guitar cord, the way you might do with a rope. Longitudinal waves (also called pressure waves): only need one dimension to move. Although sound moves out from its source spherically, it is in fact a longitudinal wave, this is why sound can move through walls: the vibrating air is able to vibrate the wall, which in turn vibrates the air on the other side. A good visual demonstration of this phenomenon is one of those "executive time wasters" that has several steel balls hanging from a bar. When you pull the ball on one end out and let it fall back and hit the other balls, the ball on the other end flies out, leaving the balls in the middle stationary. Although the balls in the middle haven't moved, a pressure wave has moved through them, unseen to our eyes.

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Longitudinal vs. transverse waves

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Human sensitivity range to pitch and amplitude

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20 Hz (cycles per second) to 20 kHz (20,000 Hz)

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-Attack time is the time taken for initial run-up of level from nil to peak, beginning when the key is first pressed.
-Decay time is the time taken for the subsequent run down from the attack level to the designated sustain level.
-Sustain level is the level during the main sequence of the sound's duration, until the key is released.
-Release time is the time taken for the level to decay from the sustain level to zero after the key is released.

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Envelope

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A section of music

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Phase

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Interference is the way in which waves interact with each other in air or electrically. There are two types of interference: “constructive interference” and “destructive interference.” As the “compression” part of two waves come together, even greater compression is created. The compression adds up. This is “constructive interference.” If compression and rarefaction come together, they cancel out. This is “destructive interference” The effect of “flanging” is the result of both types of interference.

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Interference

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“Flanging” is an effect that results in a sweeping change of harmonic presence in a sound

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Flanging

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If a sound has many very quick repetitions (less than 80 milliseconds apart), the listener hears the phenomenon of “reverberation,” or “reverb.” When one sings in the shower, the tiles reflect the sound so that it keeps bouncing around. Because most showers are rather small, the bounced sound will reach the ear very quickly so that the ear hears the original sound followed by a smear of very quick repetitions. This “smear of very quick repetitions” is called “reverberation.”

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Reverberation

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Often defined as “tone color,” timbre is a result of the harmonic content of a sound (i.e., which harmonics are present in the sound and how strong they are). For instance, if you sing a note with the vowel “ooooooo,” and then sing the same note with the vowel “eeeeee,” you have changed the timbre of the note, but not the note. If we hear a flute and an oboe play a note (the same note), we can tell the difference between them by their harmonic content (sometimes called “spectra”). We might say, “the oboe has a brighter timbre than the flute.” This actually means that the oboe has more and stronger harmonics then the flute when playing the same pitch.

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Timbre

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The “harmonic series” is the series of pitches that occurs in long thin bodies (e.g. guitar or piano strings, or tubes, like trumpets or flutes) when they vibrate.

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The harmonic series

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Filtering is the removal of harmonics from a sound. Any time that the “harmonics” of a sound are altered, the “timbre” of that sound changes, too. A Wah-wah pedal is a device that filters out more harmonics when the pedal is pushed down, and less harmonics when the toe of the pedal comes up.

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Filtering

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Musique concrete is a type of music that is made from recorded sounds. Invented in 1948 by Pierre Schaeffer, it first tended to focus on “found sounds.” Schaeffer would collect a bunch of sound recordings (usually of the same type of object) and then bring the sounds back to his studio where he would assemble them into a piece of music. Because he was starting with the sounds that were, in fact, “concrete,” or real, he called the music Musique concrete.

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Musíque concrete

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The 5 basic tape music techniques:

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1. Loops (before ‘tape loops’ there were ‘locked-groove’ loops)
2. Cutting and splicing
3. Direction change
4. Pitch change
5. Tape delay

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a device that converts one type of energy to another

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Transducer

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the repetitive variation, typically in time, of some measure about a central value (often a point of equilibrium) or between two or more different states. Familiar examples include a swinging pendulum and AC power.

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Oscillators

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changes the pitch

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Frequency modulation

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changes the loudness

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Amplitude modulation

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alters the harmonic content

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Timbre modulation