The Poème des Montagnes op. 15 (1881) for piano deserves mention because it is one of a number of works concerned with aspects of nature, a source of evocatory stimulus upon d'Indy in a number of instances. There are romantic qualities of some grandeur in these pieces, as well as dramatic vitality in one idea which d'Indy appropriately used in a later work,[52] but as a whole they do not rank with his best music. If a poetic mood is apparent in Saugefleurie op. 21 (1884) and a vein of piquant fancy is to be found in the suite op. 24 for trumpet, flutes and strings, both are not unjustly to be ranked chiefly as steps leading to works of larger significance.
After Le Chant de la Cloche, whose performance brought instant recognition to d'Indy, the 'Symphony on a Mountain Air' op. 25 (1886) for piano and orchestra is the first instance of d'Indy's deliberate resolve to follow in the footsteps of Franck as regards formal and thematic treatment. The basis of the work is a true folk-song[53] which furnishes through rhythmic and melodic modification the principal themes of the symphony. Here we find more assertive individuality than in any instrumental work since the Wallenstein trilogy, a genuine capacity for logical developments, thoughtful sentiment in the slow movement, and great animation in the vivid Kermesse which forms the finale. Similarly the trio op. 29 (1887) for clarinet, violoncello and piano adopts the Franckian method while permitting an equal freedom of personal idiom. Again passing over minor works for the piano, a few choral or vocal pieces which have a contributory rather than a capital import, and leaving momentarily the opera Fervaal, d'Indy's next striking contribution to instrumental music is the set of symphonic variations Istar, op. 42 (1896). The program of the work, taken from the Epic of Izdubar, is concerned with the descent of Istar into the Assyrian abode of the dead to rescue her lover, leaving a garment or ornament with the guardian of each of seven gates, until naked she has fulfilled the test and restores her lover. Accordingly d'Indy has adroitly reversed the variations from the complex to the simple, to describe the gradual spoliation of the heroine, until the theme at last emerges in a triumphal unison depicting the nudity of Istar. The variations are in themselves of great ingenuity, of picturesque detail and gorgeous orchestral color, but the descriptive purpose is somewhat marred by the artificialities of technical manipulation. Heard as absolute music, the intrinsic qualities of the piece delight the listener and its uncompromising individuality shows the progressive maturity of the composer.
In a second string quartet, op. 45 (1897), d'Indy's inventive fertility in evolving not only the chief themes but accompaniment figures from a motto of four notes, gives further evidence of his skill along the lines suggested by Franck. Certain episodes and even entire movements give cause for suspicion that the composer was drawn to the realization of technical problems rather than that of concrete expression. The contrapuntal texture of the quartet undoubtedly proceeds from a source anterior to Franck, that of the counterpoint of the sixteenth century to which d'Indy has reverted more and more since his connection with the Schola. But it is combined with a superstructure of personal and modernistic expression upon classical and Franckian models in such a way as to achieve a notable beauty. If the Chanson et Danses, op. 50 (1898), for wind instruments, is laid out in small forms, its singular purity of style and its spontaneous mastery of a difficult medium make it of greater weight than its scope would indicate.
D'Indy's instrumental masterpiece, the Symphony in B-flat, op. 57 (1902-3), easily marks the summit of his achievement in this field. If, from a technical standpoint, it surpasses anything hitherto attained by its composer in logic and elasticity of form, subtle and compelling development of themes from its generative phrases, clarity of style despite its external complexity, its creative inventiveness, richness of detail, profundity of sentiment and genial orchestration are of equal magnitude. With the climax of the finale, a chorale derived from a theme in the introduction to the first movement, d'Indy attains a comprehensive sublimity that is not only unique in modern French music, but which is difficult to find surpassed in the contemporary symphonic literature of any nation. While the piano and violin sonata, op. 59 (1903-4), by reason of its smaller dimensions, can scarcely be compared with the symphony, the diversity and elasticity of its thematic development (on three generative phrases) as well as the concrete beauty of its substance make it one of the most distinguished examples of its class since that by César Franck.
Jour d'été à la montagne, op. 61 (1905), three movements for orchestra, with an underlying thematic unification of introduction and conclusion, after prose poems by Roger de Pampelonne, displays a balance of greater homogeneity between constructive and descriptive elements than any of d'Indy's programmistic works. The use of plain-chant themes in the movement Jour,[54] with the subtitle Après-midi sous les pins, and again in Soir, manifests not only a felicitous emotional connotation, but an increasing desire to correlate even the music of externals to spiritual sources.
The poem Souvenirs for orchestra, op. 62 (1906), an elegy on the death of his wife, is not only profoundly elegiac in sentiment, but attains an unusual poignancy through the quotation of the theme of the Beloved from the earlier Poème des Montagnes. Both in Jour d'été à la montagne and in Souvenirs d'Indy employs orchestral effects ranging from delicate subtlety to extreme force in a manner so entirely his own as to dispel forever the question of imitative features.
D'Indy's latest instrumental work, a piano sonata, op. 63 (1907), is more happy in its formal constructive unity than in a euphonious or natively idiomatic piano style. Its variations are hardly convincing music despite their technical skill; the scherzo has brilliant pages but too much of its thematic material is indifferent. The finale suffers for the same reason up to the climax and close, where the theme of the variations (first movement) and that of the finale are brought together with consummate contrapuntal perception.
To summarize, d'Indy as an instrumental composer has with sure and increasing power fused the methods of Franck, with early contrapuntal elements, and his own individualistic sentiment into music which presents the strongest achievement in this direction since that of his master. If d'Indy is sometimes dry or over-complex, his best works show a blending of the intellectual with the emotional which constitutes a persuasive bid for their durability. From a conservative standpoint it is impossible to imagine an abler unification of elements that tend to be disparate or antagonistic. As a master of the orchestra he can still hold his own against ultra-modern developments although he is relatively conservative in the forces he employs. If his piano music, including the Helvetia Waltzes (1882), the Schumanniana (1887), the Tableaux de Voyage (1889) and other pieces are, by comparison with others of his works, insignificant, the cantata Sainte Marie-Magdelène (1885), the chorus for women's voices Sur la Mer (1888), the imaginative song Lied Maritime (1896) are conspicuous instances in a somewhat neglected field.
D'Indy's development as a dramatic composer follows a natural path of evolution. Despite the success of the 'Wallenstein Trilogy,' the largeness of conception and the pregnant details of Le Chant de la Cloche op. 18 (1879-83), for solos, chorus and orchestra, text by the composer after Schiller's poem, although preceded by the dramatic experiments of La Chevauchée du Cid, op. 11 (1879), scene for baritone, chorus and orchestra; Clair de Lune, op. 13 (1872-81), dramatic study for soprano and orchestra, and Attendez-moi sous l'orme, op. 14 (1882), opéra comique in one act, came as a complete surprise. Even if d'Indy had obviously applied Wagner's dramatic procedures, with modifications, to a choral work, the variety and power of expression, the firm treatment of the whole, and the superb use of a large orchestra astounded musicians and public alike. If the influence of both Franck and Wagner could be discerned in the scenes of 'Baptism' and 'Love,' the assertive personality evident in the scenes 'Vision' and 'Conflagration' was entirely original, and the dramatic strokes in 'Death,' especially the telling use of portions of the Catholic service for the dead in vigorous modal harmonization, bespoke a composer of tragic intensity of imagination.
Another surprise came several years later, in 1897, when Fervaal, op. 40 (1889-95), an opera in three acts, text by the composer, had its première at the Théâtre de la Monnaie in Brussels. For a time the numerous and comprehensive Wagnerian obligations obscured the real qualities of the work, and prevented a judicial opinion. Resemblances were too many; a legendary subject, a hero who combined characteristics of Siegfried and Parsifal, a heroine partly compounded of Brünnhilde and Kundry, the renunciation of love as in the 'Ring' and many others. D'Indy furthermore boldly adopted the systematic use of leading-motives, and system of orchestration frankly modelled on Wagner. But though Fervaal was assimilative in underlying treatment, it was far less experimental than Chabrier's Gwendoline. It greatly surpassed the older work not only in thorough absorption of technical method, in continuity and flexibility of style, but in appropriate dramatic characterization, and in adroit manipulation of the orchestral forces. Furthermore, in the essence of the subject dealing with the passing of Pagan mythology, with redemption through suffering, and the outcome a new religious faith whose key-note was the love of humanity, d'Indy achieved a dramatic elevation whose moral force indicated an innovation in French operatic subjects. Its source was ultimately Teutonic, but its realization was concretely Gallic. Despite the manifest obligations, Fervaal not only shows a technical and dramatic skill of a high order, but a tragic note of distinctive individuality. The symbolic use of the ancient hymn Pange Lingua as typifying the Christian religion was not only a genuine dramatic inspiration but a salient instance of effective connotation. With the revival in 1912 at the Paris Opéra, when Wagnerianism was no longer an issue,[55] the intrinsic qualities of Fervaal were appreciated more on their own merits. The incidental music to Catulle Mendès' drama Medée, op. 47 (1898), showed afresh d'Indy's ability in dramatic characterization, as well as his faculty for realizing noble and tragic conceptions.