39S . LECTURE xxxtir. 



a regular or irregular succession necessarily produces the impression of sweet-, 

 ness or harshness. The same sounds, as form the best accompaniment for each 

 other, are also in general the most agreeable for melodies, consisting of 

 a succession of single notes; their intervals are, however, too large to be 

 sufficient for the purposes of music, and they require to be mixed with 

 other sounds which arc related to them in a manner nearly similar. 



The same constitution of the human mind, which fits it for the perception 

 of harmony, appears also to be the cause of the love of rhythm, or of a re- 

 gular succession of any impressions whatever, at equal intervals of time. Even 

 the attachment to the persons and places to which we are accustomed, and 

 to habits of every kiud, bears a considerable resemblance to the same prin- 

 ciple. The most barbarous nations have a pleasure in dancing ; and in this case, a 

 great part of the amusement, as far as sentiment and grace are not concerned,is 

 derived from the recurrence of sensations and actions at regular periods of 

 time. Hence not only the elementary parts of music, or the single notes, 

 are more pleasing than any irregular noise, but the whole of a composition 

 is governed by a rhythm, or a recurrence of periods of greater or less extent, 

 generally distinguished by bars, which are also the constituent parts of larger 

 periods, and are themselves subdivided into smaller. An interruption of tlie 

 rhythm is indeed occasionally introduced, but merely for the sake of con- 

 trast; nearly in the same manner as, in all modern pieces of music, discords 

 are occasionally mixed with concords, in order to obtain an agreeable variety 

 of expression. 



In a simple composition, all the intervals are referred to a single funda- 

 mental or key note. Thus, any air which can be played on a trumpet or on a 

 bugle horn, must consist of the harmonics of a single sound only : andwhen an 

 accompaniment is performed by a French horn, the length of the instrument is 

 fust adjusted to the principal note, and all the sounds which it is to produce 

 are selected from this natural series. But the notes constituting the most 

 natural scale are not, without exception, comprehended among the har- 

 monics; they are, however, all immediately dependent on a similar relation. 

 A sound of which the vibrations are of equal frequency with those of another, 

 is called a unison; if two vibrations occur for every one of the fundamental 

 note, the sound is called its superior octave, being the eighth of those 



