​INSTRUMENT (Lat. Instrumentum, Ital. Stromento). In general language, a tool, that by means of which work is done; hence, in music, an apparatus for producing musical sounds. Numerous as are the various kinds of instruments in practical use at the present day, they form but a small proportion of the immense number which have been invented and used from time to time. Out of nearly 340 different kinds mentioned in a list in Koch's Musikalisches Lexicon (art. 'Instrument') only 67 are given as being in use at present, and some even of these are merely varieties of the same genus. Various causes have contributed to the survival of certain instruments and the extinction of others. Quality of tone would of course be a powerfully operating cause, and practicableness in a mechanical sense would be scarcely less so; but besides this, the various ways of combining instruments in performance which prevailed at different periods, had the effect of proving certain of them to be unnecessary, and so indirectly tended to abolish them. Thus before the time of Lully it was customary for the most part to combine instruments of the same class only, and we read of a 'Concert of Violins,' 'Concert of Flutes,' etc.; this fact rendered necessary flutes of deeper compass than are now used, and accordingly we find tenor and bass flutes, extending downwards to F on the fourth line of the bass stave.^[1] So soon however as the combination of wind and stringed instruments was found to be preferable, the feeble bass of the flute would be insufficient and unnecessary, and the larger kinds of flutes naturally enough fell into disuse.

All musical sounds are the result of atmospheric vibrations; and such vibrations are excited either directly, by blowing with suitable force and direction into a tube, or indirectly, by agitating an elastic body, such as a stretched string, whereby it is thrown into a state of vibration, and communicates its own vibrations to the surrounding air. One or other of these two is the acting principle of every musical instrument. On tracing the history of the two it does not appear that either is of earlier date than the other; indeed tradition with respect to both carries us back from history into myth and fable, the invention of the earliest form of stringed instrument, the Lyre, being attributed to the god Mercury, who finding the shell of a tortoise cast upon the bank of the Nile, discovered that the filaments of dried skin which were stretched across it produced musical sounds; while the invention of the tibia or pipe—the earliest form of which is said to have been made (as its name implies) from the shank-bone of a crane—is variously ascribed to Pan, Apollo, Orpheus and others.

To attempt to describe, however briefly, all the various kinds of instruments which have been in use from the earliest ages to the present day, would extend this article far beyond its due limits. It will only be possible to mention those which are still of practical importance, referring the reader for a fuller description to the articles under the headings of their various names, and for the earlier and now obsolete kinds to Hawkins's History^[2] of Music, which contains copious extracts from the works of Blanchinus, Kircher, Luscinius, and others, illustrated by wood-cuts.

In all essential respects, instruments may be divided into three classes; namely, wind instruments, the descendants of the pipe; stringed instruments, descended from the lyre; and instruments of percussion. This classification, which is of considerable ^[3]antiquity, is not entirely satisfactory, as there are certain modern instruments which can scarcely be classed under any one of its heads without confusion for instance the Harmonium, which although played by wind, is not strictly a wind-instrument, since ​ ​are played by percussion—the Pianoforte and the Dulcimer; in the former the strings are struck by hammers attached to the keys, and in the latter by two hammers held in the hands.

3. Instruments of Percussion (Ger. Schlaginstrumente; Ital. Stromenti per la percussione; Fr. Instruments à percussion). These are of two kinds, those whose chief use is to mark the rhythm, and which therefore need not, and in many cases do not, give a note of any definite pitch, and those which consist of a series of vibrating bodies, each giving a definite note, so that the whole instrument possesses a scale of greater or less extent. Of the instruments of indefinite pitch, some are struck with drumsticks or other suitable implements; these are the Bass Drum, Side Drum, Tambour de Provence, Gong or Tam-tam, and Triangle; others, such as Cymbals and Castagnettes, are used in pairs, and are played by striking them together; and one, the Tambourine, or Tambour de Basque, is struck with the open hand. The instruments of percussion which give definite notes, and which are therefore musical rather than rhythmical, are the Kettle Drums (used in pairs, or more), Glockenspiel (bells used in military bands and occasionally with orchestra), and the Harmonica, consisting of bars of either glass, steel, or wood, resting on two cords and struck with a hammer.

4. There are still one or two instruments to be mentioned which are not easily classed in any of the three categories just described. In the Harmonium, which we have accepted as a windinstrument, the sound is really produced by the vibrations of metal springs, called reeds, though these vibrations are certainly excited and maintained by the force of wind; so also stretched strings may be acted upon by wind, and of this the Æolian Harp is an illustration. [See Æolian Harp.] The instrument or organ of Mr. Baillie Hamilton, which is said to be a combination of tongue and string, is not sufficiently perfected to be described here.

Metal tongues or reeds may also be played by plucking, and this method is employed in the so-called Musical Box, in which a series of metal tongues are plucked by pins or studs fixed in a revolving barrel. Another instrument played by plucking, but possessing only a single reed or tongue, is the Jews-harp. In respect to the production of its various notes this instrument differs from all others. It is played by pressing the iron frame in which the reed is fixed against the teeth, and while the reed is in a state of vibration altering the form of the cavity of the mouth, by which means certain sounds of higher pitch than the fundamental note may be produced, and simple melodies played. These higher sounds appear to be upper 'partial-tones' of the fundamental note of the reed, which are so strongly reinforced by the vibrations of the volume of air in the mouth as to overpower the fundamental tone, and leave it just audible as a drone bass. In the Harmonica proper, another mode of sound-production is employed, the edges of glass bowls being rubbed by a wetted finger. [See Harmonica.]

For much of the information contained in this article the writer is indebted to Schilling 'Universallexicon der Tonkunst.'