3.3 Modes and ragas: more than just a scale  (Page 2/5)

[link] shows two scales and two modes. The two major scales use different notes, but the relationship of the notes to each other is very similar. For example, the pattern of half steps and whole steps in each one is the same, and the interval (distance) between the tonic and the dominant is the same. Compare this to the two church modes. The pattern of whole steps and half steps within the octave is different; this would have a major effect on a chant, which would generally stay within the one octave range. Also, the interval between the finalis and the dominant is different, and they are in different places within the range of the mode. The result is that music in one mode would sound quite different than music in the other mode. You can't simply transpose music from one mode to another as you do with scales and keys; modes are too different.

The classical greek modes

We don't have any recordings of ancient music, so we do not know exactly what it sounded like. But we can make some educated guesses as to what music from ancient Greek and Roman times really sounded like, based on their writings. We know, for example, that they used modes based on tetrachords , mini-scales of four notes, in descending pitch order, all contained within a stretch of a perfect fourth . We have very detailed descriptions of tetrachords and of Greek music theory (for example, Harmonics , written by Aristoxenus in the fourth century B.C.).

The perfect fourth is an interval that occurs naturally, for example in string and wind instrument harmonics (see Standing Waves and Musical Instruments for more on this), so we can be pretty certain that we understand that part of ancient Greek music theory. It is more difficult to be certain of the exact tuning of each note within a tetrachord. Enharmonic tetrachords are particularly confusing; it is clear that two of the notes were very close in pitch. As shown in [link] , they are often notated so that, using modern tuning, the two notes would sound the same. This sameness is a result of equal-tempered tuning, however; other tuning systems have been used which cause enharmonic notes to be tuned slightly differently. (See Tuning Systems for more about this.) It is not clear whether these ancient tetrachords actually had only three distinct pitches (it would not be the only time that something existed only to make a theory seem more consistent), or whether the two "enharmonic" notes were actually slightly different. References to "shading" in some of the ancient texts may have referred to differences in tuning.

Tetrachords

Since a tetrachord fills the interval of a perfect fourth , two tetrachords with a whole step between the end of one and the beginning of the other will fill an octave. Different Greek modes were built from different combinations of tetrachords.