against the marble.  To produce this effect, the composer uses the xylophone with capital results.  But of all the ordinary instruments of percussion, the only one that is really musical and deserving of comment is the kettle-drum.  This instrument is more musical than the others because it has pitch.  Its voice is not mere noise, but musical noise.  Kettle-drums, or tympani, are generally used in pairs, though the vast multiplication of effects by modern composers has resulted also in the extension of this department of the band.  It is seldom that more than two pairs are used, a good player with a quick ear being able to accomplish all that Wagner asks of six drums by his deftness in changing the pitch of the instruments.  This work of tuning is still performed generally in what seems a rudimentary way, though a German drum-builder named Pfund invented a contrivance by which the player, by simply pressing on a balanced pedal and watching an indicator affixed to the side of the drums, can change the pitch to any desired semitone within the range of an octave.

The tympani are hemispherical brass or copper vessels, kettles in short, covered with vellum heads.  The pitch of the instrument depends on the tension of the head, which is applied generally by key-screws working through the iron ring which holds the vellum.  There is a difference in the size of the drums to place at the command of the player the octave from F in the first space below the bass staff to F on the fourth line of the same staff.  Formerly the purpose of the drums was simply to give emphasis, and they were then uniformly tuned to the key-note and fifth of the key in which a composition was set.  Now they are tuned in many ways, not only to allow for the frequent change of keys, but also so that they may be used as harmony instruments.  Berlioz did more to develop the drums than any composer who has ever lived, though Beethoven already manifested appreciation of their independent musical value.  In the last movement of his Eighth Symphony and the scherzo of his Ninth, he tunes them in octaves, his purpose in the latter case being to give the opening figure, an octave leap, of the scherzo melody to the drums solo.  The most extravagant use ever made of the drums, however, was by Berlioz in his “Messe des Morts,” where he called in eight pairs of drums and ten players to help him to paint his tonal picture of the terrors of the last judgment.  The post of drummer is one of the most difficult to fill in a symphonic orchestra.  He is required to have not only a perfect sense of time and rhythm, but also a keen sense of pitch, for often the composer asks him to change the pitch of one or both of his drums in the space of a very few seconds.  He must then be able to shut all other sounds out of his mind, and bring his drums into a new key while the orchestra is playing—­an extremely nice task.

[Sidenote:  The bass drum.]

The development of modern orchestral music has given dignity also to the bass drum, which, though definite pitch is denied to it, is now manipulated in a variety of ways productive of striking effects.  Rolls are played on it with the sticks of the kettle-drums, and it has been emancipated measurably from the cymbals, which in vulgar brass-band music are its inseparable companions.