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'''Rather than deal with everything in absolute frequencies, note names are used to keep things from becoming complicated.''' Because the octave is so harmonic, it is treated harmonically equivalent. Once the octave is reached, the note names repeat, and for harmonic purposes they are treated identically. In common Western music, there are only 12 possible notes in one octave. And the most common scales music only use uses 7 of those notesin any particular musical idea. A limited set of notes is known as a <u>scale</u>, which drives the possible harmony. This does not mean the composer/performer is strictly limited to those fundamental frequencies. It is simply used to provide a simplifying an easily-understood framework to build upon, like tempo. Later we will explore why Western music uses the 12 tones per octave and discuss common intervals, chords, and progressions.
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<u>Harmony</u> is the pattern of how frequencies interact. Most natural sounds are relatively noisy - they contain a random selection of frequencies. The true definition of noise is sound with equal distribution of all audible frequencies. Consider an untuned radio or TV, which produces white noise - you cannot "zero-in" on any particular frequency, although your brain may try. Noise is chaos, and all true noise is undifferentiatable from other true noise, regardless of its source. Conversely, a sine wave represents a single specific frequency. Again, this is more easily understood by our minds - we can recognize it easily and even recreate it vocally. Most instruments are designed to sound such distinct frequencies, called <u>pitches</u>, which correspond to certain [[#Notes and Movement|<u>notes</u>]]. '''Rather than deal with everything in absolute frequencies, note names are used to keep things from becoming complicated.''' Harmony is concerned mostly with the interaction of multiple notes - 2 or more notes combine to form a unique waveform, which we can perceive.
''Note: popular instruments do not create a pure, single frequency, but a multitude of frequencies (and noise) when trying to sound a note. However the lowest frequency produced is called the fundamental frequency and usually the strongest. The additional frequencies are "overtones" of the fundamental frequency. This is discussed further in [[#Timbre|timbre]] below.''
When different notes are combined, they produce different waveforms. Two different notes played simultaneously is known as an <u>interval</u>. Three or more is known as a <u>chord</u>. Some intervals and chords are perceived as being more harmonic than others. This is driven by the ratio of the fundamental frequencies involved. We have already mentioned that a 4th interval is 4/3 higher than the base frequency. A 5th interval is 3/2 the base frequency. Basically, the simpler the ratio between the frequencies can be represented, the more harmonic the two notes are. The simplest ratio is an <u>octave</u> - which contains 2x (2/1) the original pitch.
Another topic for the composer is ''arrangement''. Arrangement describes applying some musical idea into a selection of instruments. For example, if you were arranging a piece for flute, piano, and bass, you would likely have the flute play the melody, the piano playing chords, and the bass usually playing the root note of the chords. Naturally, melody is usually given a higher-pitch than the other instruments, and the root note of chords is usually played in the lowest-frequencies. We could come up with different arrangements that are harmonically equivalent; however, they would likely be less enjoyable to listen to.