I will cite in connection with the subject of the "appoggiatura" the beautiful duo with chorus of the "Passion According to St. Matthew," and at the same time, I would point out the error committed in making of this passion a most grandios performance with grand choral and instrumental masses. One is deceived by its noble character, by its two choruses, by its two orchestras, and one forgets that it was destined for the little Church of St. Thomas in Leipsig, where Sebastian Bach was organist. While in certain cantatas that composer employed horns, trumpets, trombones and cymbals, for the "Passion According to St. Matthew," he only used in each of the orchestras two flutes, two hautbois, changing from the ordinary hautbois to the hautbois d'amour and the hautbois of the chase,--now the English horn; that is to say, hautbois pitched a third and a fifth lower. These two orchestras and these two choruses then certainly were reduced to a very small number of performers. In all very ancient music, from the time of Lully, one finds constantly a little cross marked over the notes. Often this certainly indicates a trill, but it seems difficult to take it always to mean such. However, perhaps fashion desired that trills should thus be made out of place. I have never been able to find an explanation of this sign, not even in the musical dictionary of J. J. Rousseau. This dictionary none the less contains a great deal of precious information. Does it not inform us, among other things, that the copyists of former times were veritable collaborators? When the author indicated the altos with the basses, the hautbois with the violins, these copyists undertook to make the necessary modifications. Times have unfortunately changed since. In Rameau's music, certain signs are unintelligible. Musical treatises of that time say that it is impossible to describe them, and that to understand them it was necessary to have heard them interpreted by a professor of singing. With clavecinists the multiplicity of grace notes is extreme. As a rule they give the explanation of these at the head of their works, just as Rameau did. I note a curious sign which indicates that the right hand should arrive upon the keys a little after the left. This shows that there was not then that frightful habit of playing one hand after the other as is often done nowadays. This prolixity of grace notes indulged by players upon the clavecin is rather terrifying at first, but one need not be detained by them, for they are not indispensable. The published methods of those times inform us in fact that pupils were first taught to play the pieces without these grace notes, and that they were added by degrees. Besides, Rameau in transcribing for the clavecin fragments of his operas, has indicated those grace notes which the original did not contain.