Routh’s style evolved slowly. The first works to achieve professional performance and acceptance were songs. Four Shakespeare Songs were commissioned by the lieder singer Ilse Wolf for a tour of Germany in 1963. This collaboration proved very successful and led to further songs, notably Elegy and Songs of Farewell , as well as the Yeats settings A woman young and old, which were first sung by Wolf’s pupil Noelle Barker. The idiom of these early songs is freely chromatic, the tonality explicit. In the instrumental and orchestral works which followed in the 1970s, freedom in the development of the material tended to lead in one of two directions ; at a fast tempo it led towards the use of semitones in the melodic and harmonic movement , making for short sentences and tautness of structure ; at a slow tempo it led towards the use of whole tones, making for an impressionistic texture and a more measured rate of harmonic change. This resulted in a poetic element of free association and fantasy. Whatever the chosen structure, Routh’s style has always been guided by a strong sense of harmonic direction and movement. Works of this time which colourfully display the characteristics in both these respects are the Cello Concerto and the Double Concerto.

By the late 1970s, with such brilliant works as Mosaics and the Oboe Quartet, both of which were widely played in Europe, particularly in Germany, his style had reached a turning point. The early freedom , and the expressive qualities to which it gave rise, became more strictly formulated; and the musical language began to be governed by a mode which took into account both the trends mentioned. This mode consisted of nothing other than the whole tone scale, but with the addition of the perfect fourth. Routh first used this mode as such in the piece for solo oboe Tragic Interludes of 1982, in which each short section bases the mode on a different degree of the scale, or tonal centre. It had been foreshadowed in many works before then, such as the organ piece Lumen Christi of 1968 ; but its uncompromising use in Tragic Interludes opened the door to a great wealth of musical opportunities, which led to such major compositions as the Oboe Concerto and Celebration for piano. The acceptance of the discipline implied by the new mode led immediately to greater extension of its use. Further possibilities appeared, chiefly of fresh large-scale structures, and the gradual evolution of a new form of impressionism, based on an extended tonality. These discoveries bore fruit in some of Routh’s large-scale orchestral works of the 1980s, notably Scenes for Orchestra I and Poème Fantastique.

 Many of Routh’s compositions were composed with specific performers in mind, with whom he was in close artistic rapport. The technical accomplishments of particular artists and groups have always been important to him. Virtuosity is not merely something he admires . It is almost something he sees as an integral part of the musical idea itself. A performance which lacks virtuosity will be an inadequate realisation of the composer’s musical vision. The early songs had as their starting point the vocal purity and expressiveness of Ilse Wolf’s lieder singing. Similarly the instrumental works which followed, those for violin and cello, which occupied much of the late 1960s and early 1970s, were inspired by the violin playing of Maria Lidka, and the cello playing of Christopher Bunting, representing as they did the school and tradition of Max Rostal and Pablo Casals respectively.

The piano, which he studied from an early age, has always been the basis of his composition from the start. Not only does he compose at the piano, but the instrument has been the source of many virtuoso works, both for solo piano and concertos. Fresh musical ideas and the working out of large-scale structures have often found their first outlet in a work for piano. The artists who have chiefly inapired him , and with whom he has worked closely, were in the 1980s the American pianist Jeffrey Jacob, and in the 1990s the Bulgarian pianist Lora Dimitrova. Each combined a stunning technique with sensitivity, the one in the American, the other in the Russian tradition. Routh also uses the piano as a part, and a very individual part, of the orchestral ensemble. Among the prime examples of this are Spring Night , Scenes for Orchestra I and Symphony I. If the origin of this concept lies in the neoclassical aesthetic of Stravinsky, it is to that same composer also that Routh owes the rhythmic articulation and the secco style of piano playing which is called for in many of the ensemble pieces and duos, such as the Diversions for violin and piano, and the Symphonic Variations in their clarinet and piano version. In the Concertos for Ensemble ,which he composed in the 1980s and early 1990s as pieces in Divertimento style for the soloists of the Redcliffe Ensemble, the pianist is called on for just such a distinctive style of playing. The piano in fact is the focal instrument of the group, like the continuo in the baroque period.

Routh’s organ music stands somewhat apart from the rest of his output. Not only does the instrument itself make special technical demands on the composer, but the resulting structures are unlike his other compositions. From the start, ever since his student days at Kimg’s College, Cambridge, when he first became acquainted with it, he was fascinated by the organ simply as a source of sound, rich and varied at each end of the dynamic spectrum, with a huge range of colour and full of traditional association. Indeed colour and tradition are the distinguishing features of his two chief compositions for organ, A Sacred Tetralogy (1959-1974), four symphonic organ works for the principal seasons of the Church’s year, and Four Marian Antiphons (1988-1989). He uses plainchant in organ composition, not elsewhere. He sees the long tradition of Gregorian plainchant as being appropriate in organ music, and the composer’s function as being to integrate this into the greatly enlarged colour and power of the modern organ, and the extended tonal idiom.

His organ style has two aspects. First, that of chamber music; the clear, linear texture of a contrapuntal keyboard instrument, full of vitality, colourful registration, and articulation in attack. The prototype of this is the Trio Sonata and Chorale Prelude of the baroque period. Second, that of less direct sonorities, calling for space and a reverberant acoustic. This is the fuller, more remote sound associated with the music of the Romantic period , particularly of the French tradition. Routh mixes both, and in so doing calls for extreme virtuosity on the part of the performer, to say nothing of the right instrument in the right building.