With regard to the grouping of movements, Corelli’s sonatas show several varieties.  The usual number, however, was four, and the order generally—­slow, fast, slow, fast.  Among the forty-eight (Op. 1, 2, 3, and 4, published 1685, 1690, 1694, and 1700 respectively) we find the majority in four movements, in the order given above[2]; of the twelve in Op. 3, no less than eleven have four movements, but—­

No. 1 (in F) has Grave, Allegro, Vivace, Allegro. 
No. 6 (in G), Vivace, Grave, Allegro, Allegro. 
No. 10 (in A minor), Vivace, Allegro, Adagio, Allegro.

There are, however, eight sonatas consisting of three movements; and as this, a century later, became the normal number, we will give the list:—­

Op. 1, No. 7 (in C) Allegro, Grave, Allegro. 
                               (Middle movement begins in
                               A minor, but ends in C.)

Op. 2, No. 2 (in D minor) Allemanda (Adagio)
                               Corrente (Allegro), Giga
                               (Allegro).

Op. 2, No. 6 (in G minor) Allemanda (Largo), Corrente,
                               Giga.

Op. 2, No. 9 (F sharp minor) Allemanda (Largo). 
                               Tempo di Sarabanda (Largo). 
                               Giga (Allegro).

Op. 4, No. 8 (D minor) Preludio (Grave). 
                               Allemanda (Allegro). 
                               Sarabanda (Allegro).

Op. 4, No. 10 (G) Preludio[3] (Adagio) and Allegro. 
                               Adagio and Grave (E minor). 
                               Tempo di Gavotta (Allegro).

Op. 4, No. 11 (C minor) Preludio (Largo). 
                               Corrente (Allegro). 
                               Allemanda (Allegro).

Op. 4, No. 12 (B minor) Preludio (Largo). 
                               Allemanda (Presto). 
                               Giga (Allegro).

It is interesting to note that each of the two sonatas (Op. 1, No. 7, and Op. 4, No. 10), most in keeping with its title of sonata, has the middle movement in a relative key.  Op. 1, No. 7, begins with an Allegro in common time; and the short Grave is followed by a light Allegro in six-eight time.  The first movement, with its marked return to the principal key, is very interesting in the matter of form.  The other sonatas with suite titles have all their movements in the same key.  Locatelli in his XII Sonate for flute, published early in the eighteenth century, has in the first:  Andante, Adagio, Presto; also Nos. 3, 5, etc.  So, too, in Tartini’s Sonatas (Op. 1) there are also some in three (No. 3, etc.).  But Emanuel Bach commenced with that number, to which, with few and unimportant exceptions, he remained faithful; likewise to the slow movement