What, however, was for the ancients not proverbially, but literally, a jump a dorio ad phrygium—­namely, the contrast between D-minor and E-minor—­is for us no longer such a very astonishing antithesis.  In the seventeenth century Prinz finds the same Dorian key—­which for Aristotle bore the stamp of dignity and constancy—­as D-minor, not only “grave” but also “lively and joyous, reverent and temperate.”  This key conveys to Kircher’s ear the impression of strength and energy.  For Matheson it possesses “a pious, quiet, large, agreeable and contented quality,” which encourages devotion and peace of mind, and, for that matter, may also be employed to express pleasure.  On the other hand, since Ch.  P. Schubert’s theoretical procedure and since the use Gluck and Mozart have made of D-minor in dramatic practice, the modern esthetic critic finds the stamp of womanly melancholy, dark brooding, deep anxiety, in the selfsame key which for a former age was the tonus primus, the one particularly expressive of manly dignity and strength.  And, to cap the climax, the ear of the musical Romanticist of our day has become quite accustomed also to hear in D-minor devilish rage and revengeful fury, as well as all sorts of demoniacal terror and dreadful, midnight, musical vampirism, as, for example, we find the Queen of Night giving vent in D-minor to the “hellish revenge” which boils in her heart, and in the Freischuetz hell triumphs in D-minor.  In the seventeenth century, Sethus Calvisius, speaking of C-major, the Ionian key, says it was formerly a favorite key for love songs and therefore had acquired the reputation of being a somewhat wanton and lewd melody; in his day, on the contrary, it resounded clear, warlike, and was used to lead the warriors in battle.  The victoriously joyful battle hymn of the Protestant church, “A mighty fortress is our God,” is therefore in the Ionian key.  Calvisius himself is, however, puzzled at this incredible transformation in the conception of the selfsame thing, and adds that one is almost inclined to suspect that what is now known as the Ionian key was formerly called the Phrygian, and vice versa.  The fact is, however, that the names have not changed—­it is the ear which has changed.  If before Calvisius C-major was the erotic key, in the seventeenth century G-major was considered so; in the eighteenth, on the contrary, when love poetry jumps from the merry and playful over to the sentimental, the musical ear likewise altered accordingly, and even before the time of Werther and Siegwart the languishing, gently melancholy G-minor was the fashionable tone, for the erotic Matheson, indeed, even goes so far as to declare that it is the “most beautiful of tones”—­an opinion which is certainly characteristic of the state of nerves of the world of culture at that day.  We have outgrown this tearful, tender love melody and now consider A-major to be a key especially appropriate for the love song; and already we find Don Juan declaring his love to Zerlina in A-major.