Corelli’s opus 5 was published in Rome in 1700. The four earlier _opera_ and the _concerti grossi_ of 1712 occupy a place in the development of chamber and symphonic music. The opus 5 may be taken as the solid foundation of violin music, that is music for a single violin with accompaniment. It consists of twelve solo sonatas, with figured bass for harpsichord, 'cello, or theorbo. The first six of these are similar in spirit to the _sonate da chiesa_. They are generally serious in treatment. The other six correspond to the _sonate da camera_. Five of them are made up of dance movements in the style of a suite, though the order is irregular, and here and there the dance name is not written in the score. The last consists of variations on a melody known as _La folia_. The melody is very old. The sarabande rhythm suggests an origin in connection with some sort of Spanish dance; and in a series of Spanish dances published in 1623 there is a _Follie_. Also the French clavecinist d’Anglebert wrote a series of variations which he published in his set of clavecin pieces (1689) as _Folies d’Espagne_. It is very doubtful that this melody, of which Corelli and Vivaldi as well made use, was composed by G. B. Farinelli, though in England it was known as ‘Farinelli’s Ground.’ Rather it is one of the old popular songs, such as _La romanesca_, which composers employed as a _basso ostinato_ in sets of divisions or variations, very much like a Chaconne or a Passacaglia. The treatment of the violin in these twelve sonatas has, and well may have, served as a model during the years which have passed since they were written. Music cannot be conceived more fitting to the instrument. It is true that none calls for brilliant virtuosity. Corelli never goes beyond the third position; but within this limit no effect in sonority or delicacy has been neglected. The polyphonic style of the first six is worth mentioning. It will be observed that in all the first allegros, and in the last as well, the violin is given a certain amount of two-part music to play. Usually there is a strong suggestion of fugal style. The violin announces the subject, and continues with the answer. Then the figured bass takes it up. The first allegro in the fourth sonata offers a clear example. Throughout the entire movement the instrument is called upon to play more or less in polyphonic style--carrying _two_ parts. It is, however, a graceful and flowing style. There is no suggestion of learning too heavy for sound. The short, slow preludes at the beginning of each sonata are all beautifully wrought. The smooth imitations in No. 2, the use of a rhythmical figure in the bass of No. 3, and in all the free independent movement of the two parts, speak of a composer of finest instinct and true skill.