In principle, the string quartet has existed since the sixteenth century, when madrigals[33] and _frottole_ written in vocal polyphony and for vocal execution were adapted to instruments. The greater part of the polyphonic works of the fifteenth and sixteenth centuries was written in four parts, and so were the German _lieder_, French _chansons_, and Italian _canzonette_, as well as the dance pieces of the sixteenth and seventeenth centuries. In instrumental music four-part writing has never been superseded, despite the quondam preference for many voices, and the one hundred and fifty years’ reign of Figured Bass. But a strictly four-part execution was adhered to less and less, as orchestral scoring came more and more into vogue for suite and sonata. Hence the string quartet, when it reappeared, was as much of a novelty in its way as the accompanied solo song seemed to be in 1600. _Quartetti_, _sonate a quattro_ and _sinfonie a quattro_ are, indeed, common titles in the early seventeenth century, but their character is distinctly different from our chamber music; they are _orchestral_, depending on harmonic thickening and massed chordal effects, while the peculiar charm of the string quartet depends on purity and integrity of line in every part, and while, at the same time, each part is at all times necessary to the harmonic texture. Thus the string quartet represents a more perfect fusion of the polyphonic and harmonic ideals than any other type. The exact point of division between ‘orchestral’ and true quartets cannot, of course, be determined, though the distinction becomes evident in works of Stamitz and Gossec, when, in one opus, we find trios or quartets, some of which are expressly determined for orchestral treatment while others are not. It is Stamitz’s reform again which ‘loosened the tongue of subjective expression,’ and, by turning away from fugal treatment, prepared the way for the true string quartet. Boccherini’s first quartets are still in reality symphonies; and in Haydn’s early works, too, the distinction between the two is not clear. Boccherini’s, however, are so surprisingly full of new forms of figuration, so sophisticated in dynamic nuances, and so strikingly modern in style that, without the previous appearance of Stamitz, Boccherini would have to be considered a true pioneer.