All About Music

Pitch, Melody & Harmony

Lots of things make noises but in general bigger objects make deeper noises, whether long columns of air or long strings in a musical instrument, big chests, large animal footsteps, or simply large objects generally banging together. Conversely, smaller instruments, short columns of air, short strings, small animals or objects make higher pitched noises. We tend to find large things more threatening than smaller things (part of our evolutionary heritage) so pitch on its own can affect how we percieve sounds and music, providing a basic scale from "high = light, happy, carefree" to "low = dark, sad, ominous".
So Pitch on its own affects our perceptions.

A Melody consists of a linear sequence of tones. A good melody (even if it doesn't have words) is often one that we could hum, sing or whistle. In general we prefer melodies where the tones are reasonably close together, with a variety of nice harmonious intervals between them, and a rhythm similar to that of speach. The notes should not be in an extreme range and shouldn't have large awkward jumps between them. The notes should also have durations which are not too short and not too long (often in the range of 0.1 second to 2 seconds). In this way melodies are very similar to sentences that our brains are designed to speak and listen to, although instrumental musical can stretch those boundaries a little.

Unusual things happen when we combine tones of different pitches, called Harmony. Some combinations go well together and some don't. Those notes which combine well seem to be close to what's called the "harmonic sequence". The harmonic sequence is the completely natural set of different notes produced by something vibrating, and is most easily demonstrated musically using brass instruments. The lowest notes of this series are like those produced by a "natural" (without keys) instrument such as a bugle, and include octaves, fifths and thirds. These are just the notes which go well together to make "harmonious" sounds like major chords. On a stringed instrument you can demonstrate the lower notes of the harmonic series by playing the strongest "harmonics" of the strings which divide the length into fractions like halves, thirds, quarters, fifths, etc. These harmonics are always present to varying degrees within all notes, and their proportions help to give sounds their unique colour or tone.

A minor chord differs from a major one by using a "minor third" interval. The minor third is further up the harmonic sequence and therefore sounds remote from the original note, which goes to make the minor chord sound darker and less natural. Other combinations of notes are even more remote on this sequence and can give rise to musical clashes or "dischords". It is worth observing at this point that our equal-tempered method of dividing a music octave into 12 identical intervals produces some notes which are only approximately the exact values of the harmonic series, but nevertheless close enough to deceive most ears. Our long exposure to music based on these 12 notes means that they sound normal anyway.