This demonstration compares ascending linear and logarithmic musical scales. The frequency of a note one octave above another is twice the original frequency. Two notes which are adjacent in a scale are said to be a "semitone" apart.
A linear scale divides the octave into equal frequency steps. For the default 12-note linear scale given below, the notes range from 261.62Hz to 523.24Hz in equal steps of 21.80Hz. The ratio between the frequency of a note and the next higher note in a linear scale is variable. In a 12-note logarithmic scale, the ratio is a constant and must be the twelfth root of two (= 1.05946). After 12 steps the frequency should be twice the original frequency and (1.05946)12 = 2. Most cultures use scales which are closer to logarithmic than linear. An "equal-tempered" scale is another name for a logarithmic scale.
Diatonic scales are 7-note scales. The logarithmic 7-note scale in this demonstration is the "major" scale of Western music comprised of notes generated by multiplying the starting frequency by 1.05946 raised to the 0, 2, 4, 5, 7, 9, 11, and 12 (to complete the octave) powers.
This applet requires Java 1.1 and a sound card. The highest frequency that can be produced without aliasing problems is ~3500Hz. This demonstration was created by Dan Boye.