an instrument by which we are enabled to try the several proportions of musical sounds and intervals, as well in the natural as in tempered scales. Originally it had, as its name implies, only one string; but it is better constructed with two, as we have by means of this additional string an opportunity of judging of the harmony of two tempered notes in every possible variety of temperament (see Temperament and Tuning). It consists of a brass rule placed upon a sound-board, and accurately divided into different scales according to the purposes for which it is chiefly intended. Above this rule the strings are to be stretched over two fixed bridges, between which there is a moveable fret, so contrived as to divide at pleasure one of the strings into the same proportional parts as are engraved upon the scales beneath. The figure of the instrument, the manner of striking striking the strings so as to produce the sound, as likewise the construction of the moveable bridge, may be varied at pleasure according to the wish and ingenuity of the artist: But with the assistance of such an instrument accurately constructed, any person with a good ear may be enabled to tune a keyed instrument with sufficient precision to answer every practical purpose.
The following table contains the chief scales that have hitherto been computed. In column 1st is given the natural scale, or scale of perfect intervals. The second column contains a new tempered scale, which seems better adapted than any other to keyed instruments, when chiefly designed for lefson-playing, or playing without accompaniments. The third is a scale proposed by Mr Emerson in his Mechanics, and since recommended by Mr Jones in his Physiological Disquisitions, and by Mr Cavallo in the Philosophical Transactions for 1758. The fourth and fifth exhibit the systems of mean tones, and of equal harmony, calculated by Dr Smith for instruments of a more perfect construction than those now in use.
| Note | Natural Scale | Temperamented Scale | Emerson, Jones, &c. | Mean Tone | Equal Harmony | |------|---------------|---------------------|---------------------|-----------|--------------| | C | 1000 | | | | | | C* | 937.5 | 952.9 | 943.8 | 957 | 959.3 | | Db | 888.9 | 893.3 | 890.9 | 894.4 | 895 | | D* | 833.3 | 837.5 | 840.8 | 856 | 858.6 | | Eb | 800 | 798 | 793.7 | 800 | 801 | | Fb | 750 | 748.1 | 749.1 | 747.6 | 747.4 | | F* | 711.1 | 712.9 | 707.1 | 715.5 | 717 | | Gb | 666.7 | 668.3 | 667.4 | 668.7 | 669 | | G* | 625 | 632 | 629.9 | 640 | 641.7 | | Ab | 600 | 597 | 594.6 | 598 | 598.7 | | A* | 562.5 | 559.7 | 561.2 | 572.4 | 574.4 | | Bb | 533.3 | 533.3 | 529.7 | 535 | 536 | | B* | 500 | 500 | 500 | 500 | 500 |
N. B. Mr Jones proposes to have the two numbers which are denoted by stars respectively altered to the numbers 796 and 531.
The method of tuning any instrument by means of the monochord is as follows: First, you must tune the C of the monochord to the concert pitch by means of a tuning-fork; next, you are to put the middle C of your instrument in perfect unison with the C of the monochord: Then move the sliding fret to the next division on the scale, and proceed in the same manner with all the several notes and half notes within the compass of an octave. When this is done with accuracy, the other keys are all to be tuned, by comparing them with the octave which is already tempered. [The monochord is here supposed to be made to the pitch of C; but this may be varied at the will of the constructor.]
The curious reader who may wish for further information respecting the construction and use of monochords, will be highly gratified in perusing the appendix of Mr Atwood's Treatise on Rectilinear Motion, and Mr Jones's ingenious and entertaining observations on the scale of music, monochord, &c. in his Physiological Disquisitions.
Monochord is also used for any musical instrument that consists of only one string or chord; in this sense the trumpet marine may properly be called a monochord.