ACCIDENTALS, in music, are signs signifying that the notes to which they are attached have to be raised, lowered, or restored to their original pitch as the case may be. Thus a sharp raises a note a semi-tone, a flat (?) lowers it a semi-tone, while a natural (4) restores it once again to its former status. Each sign may also be doubled, though in the case of the double sharp, sig nifying the raising of the note by two semi-tones, the sign X is used instead of 0, indicating a double flat, signifying the lowering of the note by two semi-tones; and aserving to cor rect or cancel a preceding double-sharp or double-flat, although in modern practice a single natural () is usually considered suffi cient for this purpose. Accidentals introduced in the course of a piece apply only during the bar in which they occur, whereas when placed at the beginning of a composition, and constituting thereby what is called its signature, they govern the notes affected through out the whole of the piece; but in the latter case they are not prop erly called accidentals. For an explanation of the origin and application of the signs employed for accidentals, see under