Musics and Musical Instruments

Musical Scales

Pythagoras (1200 B.C.) found:

2 strings [1 twice the length of the other] octave
2 strings [length ratio 3/2] fifth
2 strings [length ratio 4/3] fourth

Going up a `fifth' each time he could get a whole musical scale.

One octave : from A --> A --> A

A B C D E F G A B C D E F G A B C D E F G . . . One fifth : C --> G --> D --> A --> ...

Eventually, one comes back to same note.

C . . . . ---> C

This is known of the "circle of fifths" (used in jazz)

Pythagorean Scale

NOT what we use today


Example:
220 Hz
= fundamental
440 Hz = 1 octave
660 Hz = a "fifth" above 440 Hz
660 Hz = 440 * 3/2

a fifth higher than 220 Hz: 220 * 3/2 = 330 Hz
a third higher than 220 Hz: 220 * 5/4 = 275 Hz



played at once => major chord




Musical Intervals

Interval frequency 1. Pair of matching harmony
Unison f1 ; f2 = f1 f1 with f2
Octave f1 ; f2 = 2f1 f2 with 2f1
Fifth f1 ; f2 = 3/2 f1 2f2 with 3f1
Fourth f1 ; f2 = 4/3 f1 3f2 with 4f1
Third (major) f1 ; f2 = 5/4 f1 4f2 with 5f1
Whole tone f1 ; f2 = 1.123 f1 no match
Semitone f1 ; f2 = 1.0595 f1 no match




Pythagorean Scale --> the third is off!

The Just Scale was created to fix this

  • make a major chord above
  • make a major chord below
  • continue until all notes are found

Problem: has different sizes whole steps
Fix: Smooth out using the

Equal Tempered Scale

Ch. Elster
Aug 26 14:27:03 EDT 2019