MODE, in music (1) the manner of ar ranging the tones and half-tones in a scale, this general designation being always accompanied by a qualifying adjective, as Dorian mode, minor mode. Greek music, from which our modern music has been evolved, had an elaborate system of nine modes, which were afterward extended to 15. Authorities vary considerably as to the differences between the modes; it is certain, however, that they were G the outgrowth of an earlier reek music, the basis of which was the tetrachord. A tetra chord is a short scale of four notes, one of the intervals being a half-tone and the others whole tones, for example: A was still the keynote or Mese, though no longer the middle or connecting note. Ter pander's was called the conjunct system and Pythagoras' the disjunct system. The latter as above printed constituted the Dorian mode, which may be defined as two Dorian tetrachords separated by the diazeuctic tone, embracing the compass of an octave. Terpander's system, not having this compass, cannot strictly be called a mode. Music seems to have developed on both these systems simultaneously in Greece, though finally that of Pythagoras supplanted Terpan der's and became universal.
By replacing the two Dorian tetrachords with two Phrygian or two Lydian the modes of the same name were formed.
The tetrachords were probably named after the people that originated them.
Until the time of Terpander (7th century s.c.) all Greek music seems to have been con fined to the limits of a tetrachord. The lyre, which was then used merely to give the singer the pitch, had but four strings, each capable of sounding but one note. It was tuned in one of the ways shown above, though the notes written should be understood to be merely relative, each singer tuning his lyre to suit his own voice.
Terpander increased the compass of the lyre by adding a second tetrachord to the first, using the highest note of the first for the lowest of the second, thus making an incomplete scale of seven notes.
The middle note, A, belonging to both tetra chords, was called Mese (middle) and had somewhat the function of our modern keynote. It will be noted that the two tetrachords are both Dorian, which was the characteristic and favorite Greek tetrachord rather than the for eign Phrygian or Lydian.
Pythagoras (582 a.c.) is the reputed author of the octave system (the foundation of our modern system). He probably learned it dur ing his visit to Egypt, where it is said to have been in use for many centuries before. By this system the two tetrachords, instead of having a note in common, were separated by a whole tone, called the diazeuctic tone or tone of disjunction.
These three were the principal modes. Each had two auxiliary modes, one commencing a fourth below and distinguished by the prefix hypo, the other commencing a fourth above with the prefix hyper. The complete list of the nine original modes is as follows: A convenient way to remember them is to imagine a series of scales, all of natural notes, and an octave in compass, beginning on each of the seven natural notes. It should be remem bered that the pitch is entirely relative; each of these modes might begin on the same actual sound. The Mese or Keynote is the fourth note of each scale.
On examination it will be seen that the three Dorian modes are each formed of two Dorian tetrachords, the three Phrygian modes of two Phrygian tetrachords and the three Lydian modes of two Lydian tetrachords. In the three principal modes the diazeuctic tone separates the tetrachords. In the hypo-modes it is the lowest note and in the hyper modes it is the highest note. In all the hypo and hyper modes the tetrachords are conjunct like those of Ter pander. It will he seen that two of the hypos correspond exactly with two hypers, namely, the hypophrygian and the hypodorian are the same as the hyperlydian and the hyperphrygian. It will be observed, however, that the arrange ment of the tetrachords and the diazeuctic tone are not the same.