In the same discussion (c. 6), Aristotle refers to the distinction between music that is ethical, music suited to action, and music that inspires religious excitement ([Greek: ta men êthika, ta de praktika, ta ho enthousiastika]). The last of these kinds serves as a 'purification' ([Greek: katharsis]). The excitement is calmed by giving it vent; and the morbid condition of the ethos is met by music of high pitch and exceptional 'colour' ([Greek: tôn harmoniôn parekbaseis kai tôn melôn ta syntona kai parakechrôsmena]). In a different connexion (_Pol._ iv. 3, p. 1290 _a_ 20), dealing with the opinion that all forms of government are ultimately reducible to two, viz. oligarchy and democracy, Aristotle compares the view of some who held that there are properly only two musical modes, Dorian and Phrygian,--the other scales being mere varieties of these two. Rather, he says, there is in each case a right form, or two right forms at most, from which the rest are declensions ([Greek: parekbaseis]),--on one side to 'high-pitched' and imperious oligarchies, on the other to 'relaxed' and 'soft' forms of popular government ([Greek: oligarchikas men tas syntonôteras kai despotikônteras, tas d' aneimenas kai malakas dêmotikas]). This is obviously the Platonic doctrine of two right keys, holding the mean between high and low. § 8. _The Aristotelian Problems._ Some further notices of the [Greek: harmoniai] or modes are contained in the so-called _Problems_,--a collection which is probably not the work of Aristotle himself, but can hardly be later than the Aristotelian age. What is said in it of the modes is clearly of the period before the reform of Aristoxenus. In one place (_Probl._ xix. 48) the question is asked why the Hypo-dorian and Hypo-phrygian are not used in the _chorus_ of tragedy. One answer is that the Hypo-phrygian has the ethos of action ([Greek: êthos echei praktikon]), and that the Hypo-dorian is the expression of a lofty and unshaken character; both of these things being proper to the heroic personages on the stage, but not to the chorus, which represents the average spectator, and takes no part in the action. Hence the music suited to the chorus is that of emotion venting itself in passive complaint:--a description which fits the other modes, but least of all the exciting and orgiastic Hypo-phrygian. On the contrary (the writer adds) the passive attitude is especially expressed by the Mixo-lydian. The view here taken of the Hypo-dorian evidently agrees with that of Heraclides Ponticus (_supra_, p. 10). The relation which Plato assumes between high pitch and the excitement of passion, and again between lowness of pitch and 'softness' or self-indulgence ([Greek: malakia kai argia]), is recognized in the _Problems_, xix. 49 [Greek: epei de ho men barys phthongos malakos kai êremaios estin, ho de oxys kinêtikos, k.t.l.]: 'since a deep note is soft and calm, and a high note is exciting, &c.' § 9. _The Rhetoric._