In a paper which I had the honour of reading before the Musical Association in 1924 I referred to the long and mysterious gap in English Musical History between 1240 and 1415, and attempted to begin (or to further) the task of filling it in. It would seem arguable that our attention might now be turned to the task of working steadily backwards from 1440, or whatever date we like to put down for the climax of Dunstable's career: for much of Dunstable's work is now accessible for criticism in the publications of the Trent Codices edited by Drs. Adler and Köller (vide Proceedings of the Musical Association for March, 1921) and further details of his bibliography are now coming to light. But before we can do this there is, as the late Mr. Barclay Squire said in one of the last letters he wrote to me, a preliminary period to be dealt with: for after Dunstable's English career closed (if indeed he ever had an English career, which is open to doubt) it seems to be admitted by scholars that there was a fifty years' period of stagnation, or even of decline: certainly a cessation of the proud rôle of teacher to the Netherland School. This may be so: but we are fortunate in being led by scholars of the type of M. van den Borren, who qualify their statements and do not dogmatise on admittedly scanty evidence: and they will be the first to admit that it may not have been so, that the pre-eminence of Dunstable and other English musicians may have continued through the latter part of the century, but that the evidence has been destroyed: and as an incurable optimist I insist on my right to hope that we shall be able to work at filling in this second gap from 1440 to 1490 without being forced to admit the theory of a fifty years' decline. Mr. H. B. Collins, well known to the Musical Association, will begin on the 28th of April, at a lecture before the Plainsong and Mediaeval Music Society, to fill in this gap with a paper on the anonymous “Missa O Quam Suavis” from Cambridge University Library, now in process of publication. And if we fail to reconstruct the progress of this fifty years we can then fall back, with perfect logical and historiographical propriety, upon the Decline theory, and shall be ready to admit it as the only working hypothesis.