Initially written in 1769, when at the height of his composing powers, Musical Conjectures represents Cooke’s only comprehensive pros on speculative music theory. As such it complements and informs numerous theoretically motivated musical movements and annotations now in the Cooke Collection which otherwise would make little sense. Of the several reasons put forward by Cooke for recording his theoretical ideas, the following Platonically influenced aspiration holds particular resonance within the broader context of his work at the Academy:

This perception of ‘true Harmony’ was common amongst ancient music supporters, some of whom saw the advancement of harmonic science as a means to heal the deep social problems that they perceived in wider society at that time. Although not a theme rigorously pursued by Cooke his reference to it in this context offers an insight into the practical importance attached by academicians to their efforts to uncover the theoretical and philosophical basis of music.

Cooke’s treatise would, however, never realise his lofty aims for moral renewal, not least because his apparent aspiration for it to be published was never fulfilled. The only known copy appears to have received little attention from scholars since Cooke’s death. Now housed in the Bodleian Library, Oxford (GB-Ob Tenbury MS 1344), along with two similar Academy-related treatises by Boyce and Marmaduke Overend, its obscurity is explained, in part, by its unpropitious appearance. To the unversed, the remaining copy of Musical Conjectures would appear to be a chaotic assortment of scribbled-on, variously sized papers with little coherence in terms of subject or organisation. A careful examination reveals, however, that it began as a more structured document. Initially Cooke had written in his characteristically untidy but legible hand on the recto side only of its 140 leaves. Confusion was sown over the succeeding two decades, when Cooke scrawled on most of the blank versos in differing levels of legibility to provide further ideas in support of his initial theoretical position. This bewildering outpouring of thoughts, mathematical calculations and occasional musical examples was, however, clearly not the sole manifestation of the treatise that Cooke intended to bequeath to posterity.