Taneyev "revised and signally improved the orchestration, which had not been uniformly satisfactorily... [T]hereafter, Taneyev began to avail himself of Glazunov's advice in orchestration; of course he made rapid strides in that field". Note the "of course". Glazunov had been Rimsky-Korsakov's student in orchestration as well as composition. Master contrapuntalist Taneyev's specialized field of study was counterpoint. He engrossed himself in the music of J. S. Bach, Palestrina, and such Flemish masters as Johannes Ockeghem, Josquin des Prez, and Orlande de Lassus. Eventually, he became one of the greatest of contrapuntalists. Taneyev published a gigantic two-volume treatise, Convertible Counterpoint in the Strict Style, the result of 20 years of labor. In it, the laws of counterpoint are broken down, explained, and brought into focus as a branch of pure mathematics. Taneyev used a quotation from Leonardo da Vinci as its inscription: "No branch of study can claim to be considered a true science unless it is capable of being demonstrated mathematically". An unfinished sequel on Canon and Fugue was published posthumously. Taneyev's focus on strict counterpoint strongly influenced the way he composed his music. He described this process, while discussing his dramatic trilogy Oresteia, in a letter to Tchaikovsky dated 21 June 1891: I spend a great deal of time on preparatory work, and less time on final composition. Some items I have not finished within the last few years. Important themes which are repeated in the opera, are used by me objectively, without any reference to a particular situation, for studies in counterpoint. Gradually, from this chaos of thoughts and sketches something orderly and definite begins to emerge. Everything extraneous is discarded. That which is unquestionably suitable remains. Taneyev would continue this series of contrapuntal exercises until he had exhausted every polyphonic possibility. Only then would he actually begin composing music. Rimsky-Korsakov described Taneyev's compositional process similarly, but with more telling detail: Before setting out for the real expounding of a composition, Taneyev used to precede it with a multitude of sketches and studies: he used to write fugues, canons, and various contrapuntal interlacings on the individual themes, phrases, and motives of the coming composition; and only after gaining thorough experience in its component parts did he take up the general plan of the composition and the carrying out of this plan, knowing by that time, as he did, and perfectly, the nature of the material he had at