and its melodies are contained within the octave from A to A. The division of the scale is 'harmonic,' i.e. the diapente (A to E) is below the diatessaron (E to A). Thus the final is A, and the dominant E.
Its plagal mode is called the Hypo-Æolian, and has the 'arithmetical' division, i.e. the diatessaron below the diapente. Here the final is A, and the dominant C:
3. The Hypo-Æolian Mode. Plagal.
with its diatessaron and diapente:—
The melodies in the Hypo-Æolian mode range from the fourth below to the fifth above the final A. The dominant is C in this plagal mode, according to the rule that 'the dominants of the plagal modes are always the third below the dominants of the relative authentic, unless this third happens to be B, when the nearest sound C is substituted for it,' as appears, for example, in the eighth mode.
The pitch of the authentic Æolian scale being higher than is convenient for many voices led to its being often transposed a fifth lower by the use of the B flat. The scale will thus begin on D, and the semitones (as in our modern minor scales) will fall in the same places as before, viz. between the second and third, and fifth and sixth notes of the scale.
In this position the Æolian mode is apt to be confounded with the Dorian, or first mode, with which, when thus transposed, it corresponds, except in the upper tetrachord, the semitone of which in the Dorian mode falls between the sixth and seventh notes of the scale. The transposed final is D, and the dominant A, as in the first mode, but the semitones fall (as in the untransposed position) between the second and third of the scale (E and F), and between the fifth and sixth (A and B♭).
The service-books contain hymns, antiphons, etc., which, though belonging originally to this Æolian mode, are sometimes ascribed to the two Dorian modes; and the scale of the Hypo-Dorian is the same as that of the Hyper-Æolian, but an octave lower, and having of course its own plagal character and treatment, and thus differing from the authentic Hyper-Æolian.
Examples of the Æolian mode may be found in the chorales 'Puer natus in Bethlehem,' No. 12, and 'Herzliebster Jesu,' No. 111, of Bach's '371 Choralgesänge.' The latter is from the St. John Passion. Mozart's Requiem may be said almost to begin and end with the Æolian scale, for the 'Te decet hymnus' and 'Lux Æterna' which form so prominent a feature in the first and last movements are given in the melody of the 'Tonus Peregrinus,' which is founded directly on this scale.
It may be well to state here that from the earliest date of any kind of counterpoint the ancient tones have been harmonised both in the organ accompaniment, and, for some portions of the divine service, in vocal parts; and although, from the vast quantity of Gregorian music used in the antiphonars, psalters, hymnaries, etc., of the Western churches, it is found expedient to use vocal unisons (or octaves) with organ accompaniment in all ordinary services, yet the psalm tones have for centuries been sung in the Sistine Chapel (where there is no organ nor other instrument) with vocal harmonies in three parts, to which Baini added a fourth part for the soprano. Gafforius arranged them in the 15th century, and the style of vocal accompaniment called Faux-Bourdon, in which he set them, had grown up gradually and very generally in the churches, most probably from the first invention and subsequent improvements of the organ. Some intimations of this are contained in the 'Micrologus' of Guido Aretino, written in the latter part of the 11th century.
ÆOLINA. A small and simple 'free reed' instrument, invented about 1829 by Messrs. Wheatstone. It consisted of a few free reeds, which were fixed into a metal plate and blown by the mouth. As each reed was furnished with a separate aperture for supplying the wind, a simple melody could of course be played by moving the instrument backwards and forwards before the mouth. Its value for artistic purposes was nil; its only interest is a historical one, as being one of the earliest attempts to make practical use of the discovery of the free reed. The æolina may be regarded as the first germ of the Accordion and Concertina.
ÆOLODION, or ÆOLODICON (also called in Germany Windharmonika), a keyed wind-instrument resembling the harmonium, the tone of which was produced from steel springs. It had a compass of six octaves, and its tone was similar to that of the harmonium. There is some controversy as to its original inventor; most authorities attribute it to J. T. Eschenbach of Hamburg, who is said to have first made it in 1800. Various improvements were subsequently made by other mechanicians, among whom may be named Schmidt of Presburg, Voit of Schweinfurt, Sebastian Müller (1826), and F. Sturm of Suhl (1833). The instrument is now entirely superseded by the harmonium. A modification of the æolodion was the æolsklavier, invented about 1825 by Schortmann of Buttelstädt, in which the reeds or springs which
