From the preface of a book about composition:
Some readers may wonder why I have decided to write about music when so many exceptional scholars have already done so—especially now, when music has become a free-for-all and composers refuse to follow any rules or principles.
The book is Gradus ad Parnassum, published by Johann Joseph Fux in 1725. The translation is mine (and a bit loose); the original reads:
Mirabuntur fortassis nonnulli, cùm tot præstantissimorum Virorum exstent monumenta, qui de Musica perquàm doctè, & abundanter scripserunt, cur ego ad hoc scribendi genus me contulerim, hoc maximè tempore, quo, Musicâ ferè arbitrariâ factâ, Compositores nullis præceptis, nulisque institutis obstringi volentes[....]
You can see the original edition at Google Books. (Via Anatoly.)
Incidentally, does anybody know for sure whether the Gradus in the title is intended to have a short u (singular ‘step’) or long (plural ‘steps’)?