Traditionally, pentatonic scales come from Europe and West Asia, but heptatonic (7-note) scales were used primarily in the Middle East and India. Above that point, most of the effects have more to do with culture than how the ear works.Īlso, about scales. From there upwards, it reaches what's called the critical band, which is a continuum of decreasing dissonance. Above the Limit of Discrimination, though, there is a sensation of hearing two pitches instead of just one. This point is arbitrary and depends on things like the absolute values of the two pitches (for example, lower pitches are harder to discriminate between) and the listener theirself. Above 15Hz, there is an unpleasant sound until the difference between the tones' pitches reaches a point called the Limit of Discrimination. Thus if one tone is at 440 and the other is at 450, the ear will hear 445 with a "beating" sound that happens 10 times per second. As the second tone rises to 15 Hz above the first tone, the average of the two tones is heard with a beating noise with a frequency of the difference in tone. While the tones are the same pitch, the sounds' amplitudes are added, which (in most situations) just makes it twice as loud. Starting with two tones that are at the same pitch, if one of the tone rises, different things happen as the interval gets wider and wider. When we listen to two intervals at the same time, we can discern differences much smaller. Daniel Levitin's book This Is Your Brain on Music also discusses pitch, and I believe that's where I read that the limit is 24 tones.Īnd, more bonus information just because I feel like you might appreciate it. If you want to read a good book that gives a lot more information than I can on the subject than I can, I highly recommend The Social Psychology of Music by Paul R. Because of this, the upward limit for number of scale tones per octave is 24. The smallest interval that can be discriminated by the ear when the two pitches are not played at the same time is about 50 cents (a quarter tone). I'm not 100% sure if that's the exact value, but it's between a fifth and a quarter tone above a fifth. although they do have an interval that is (I believe) 17 cents sharper than a sharp. For example, some scales in the folk music of places such as Java don't have a fifth in them. However, there are no universal preferences for any other intervals. Octave equivalence is universal among humans, barring neural damage or problems.
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