In many early pianos mechanical devices were added for modifying the quality of the tones, as by interposed leather strips above the hammers, or for supplementing them by independent attachments of various kinds.
The century was also somewhat prolific of experiments with peculiar keyboard instruments of a different type.
The most prominent of these was the 'harmonica,' the tones of which were produced by friction upon glass bowls. Before 1750, sets of bowls, tuned by placing water in them, were played by means of the moistened finger (as by Gluck at London in 1746), but Benjamin Franklin (d. 1790), while in London in 1763, greatly improved the contrivance by fixing the tune wholly by the size of the bowls and mounting them on a rotating axis with the lower edges in water. A keyboard was added in 1785-6 by Hessel and Röllig. Several noted players appeared, a method was issued by J.C. Müller (1788), and considerable special music written (as by Hasse, Mozart, Beethoven, etc.). Somewhat related instruments were Chladni's 'euphon' (1790) and 'clavicylinder' (1799), Leppich's 'panmelodion' (1810) and Buschmann's 'uranion' (1810).
Various efforts were made to perfect a satisfactory keyboard viol, having strings sounded by friction, as by Gleichmann (1709), Le Voirs (1740), Hohlfeld (1754), Garbrecht (1790), Mayer (1795), Kunze (1799) and Röllig (1800), but without significance.
161. The Vienna Pianists.—Associated with the Viennese
pianos, with their easy, shallow touch and their rather small,
though sensitive, tone, was a school of composers and players of
which Mozart was the type. In writing for the piano, as for
the clavichord, he selected his thematic material with instinctive
care and developed it with exquisite skill. Essential structure
was emphasized, and subsidiary or decorative material rigorously
held in check. In playing, Mozart sought for an unobtrusive
and strictly controlled style, more solicitous about precision,
clarity and smoothness than sonority, showy rapidity or complication
of effects. Mechanism of execution was simply the
means for bringing out structural values in the composition.
The piano, he evidently felt, was to be handled with caution
and restraint. If combined with other instruments, it was to be
merged in the ensemble rather than forced into extreme prominence.
The forms most used were the sonata, the chamber trio, quartet or quintet, and the concerto—all usually developed in three movements. The variation was especially popular at this period, by some writers cultivated to excess. In the hands of composers not gifted in invention the style of Mozart's day
