We have said that often he varies his key when thus repeating himself, and that such variety saves from monotony. But it must be added that even where there is no change of key he escapes being tedious to the listener. The reason must be sought in the sprightly nature of the figures he chooses, and in the extremely rapid speed at which they are intended to fly before our ears. He is oftenest a dazzling virtuoso whose music appeals to our bump of wonder, and, when well played, leaves us breathless and excited. The pieces are for the most part extremely difficult; and this, together with his ever-present reiteration of special harpsichord figures, may well incline us to look upon them as fledgling études. The thirty which Scarlatti himself chose to publish he called _esercizii_, or exercises. We may not take the title too literally, bearing in mind that Bach’s ‘Well-Tempered Clavichord’ was intended for practice, as were many of Kuhnau’s suites. But that Scarlatti’s sonatas are almost invariably built up upon a few striking, difficult and oft-repeated figures, makes their possible use as technical practice pieces far more evident than it is in the ‘Well-Tempered Clavichord’ or even the ‘Inventions’ of Bach. He undoubtedly offers the player enormous opportunity to exercise his arms and his fingers in the production of brilliant, astonishing effects. Of these effects two will always be associated with his name: the one obtained by the crossing of the hands, the other by the rapid repetition of one note. Both devices will be found freely used in the works of his father, and it is absurd to suppose that the son invented them. Yet it is hardly an exaggeration to say that he made more use of them than any man down to the time of Liszt. The crossing of the hands is not employed to interweave two qualities of sound, as it oftenest is in music for the organ or for the German and French harpsichords which have two or more manuals that work independently of each other. The Italian harpsichords had but one bank of keys, and Scarlatti’s crossing of the hands, if it be not intended merely for display, succeeds in making notes wide apart sound relatively simultaneous, and thus produces qualities of resonance which hitherto had rested silent in the instrument. It has been suggested that the device of repeated notes was borrowed from the mandolin, on which, as is well known, a _cantabile_ is approximated by rapid repetition of the notes of the melody. Scarlatti, however, rarely employs it to sustain the various notes of his tune. In his sonatas it is usually, if not intentionally, effective rhythmically; as it is, unfailingly, in more modern pianoforte music. On the harpsichord, moreover, as on the pianoforte, it can make a string twang with a sort of barbaric sound that still has the power to stir us as shrieking pipes and whistles stirred our savage ancestors.