Peculiar interest attaches to this series of sounds, because in the
Middle Ages they were supposed to be the _only_ sounds admitted by the
Greeks. This accounts for the fact that B was the first note that it
was considered right to use in two forms.
=The Greek Scales=.—The Greeks did not by any means confine themselves
to these sounds, but changed the pitch of the starting note just as
we do with our scales; in other words, both of these systems might
be transposed. Therefore they not only had all the sounds at command
that we have, but as their scales were (theoretically, at least)
tuned acoustically true, they had a great many more. But their scales
were all diatonic (the scales they called Chromatic and Enharmonic
will be explained later), they were all like our natural minor. When
they said “Dorian Scale” they meant just what we mean when we say
scale of D minor; Phrygian Scale meant E minor; Lydian Scale, F-sharp
minor; Mixo-Lydian, G minor. In addition to these four scales there
were three that began a fourth below, one a fourth below the Dorian,
called the Hypo-Dorian, A minor; a fourth below the Phrygian, called
the Hypo-Phrygian, B minor; and a fourth below the Lydian, called
Hypo-Lydian, C-sharp minor; these were the standard scales of Greek
music. These names, Dorian, etc., were retained in the Ecclesiastical
System, but the mistake was made of supposing that the Greeks used
only the fixed sounds given by the untransposed Greater System. Hence
the Church Dorian has B natural, not B-flat; the Church Phrygian,
F natural, not F sharp; and the Church Lydian begins on F natural,
instead of on F sharp. Hence, no two church scales are alike in the
positions of the halftones.