other hand, it begins with an upward leap of a fourth, or a downward of a fifth, the first note will be the dominant and the second the tonic. There are occasional exceptions to this rule, as in the following example—
Mozart. Mass in C, No. 12.
Such exceptions are, however, extremely rare, and in these cases, the close of the subject, or the beginning of the answer, will always determine the key. In our example, if the subject began in A minor, it could not end with an implied modulation (§ 118) to G. This fugue, also, being on three subjects, the key is defined as C by the other subjects, which accompany the theme here quoted (see § 406).
30. Similar reasoning will apply to our next example—
J. S. Bach. Wohltemperirtes Clavier, Fugue 21.
![\relative f' { \key bes \major \time 3/4 \mark \markup \tiny { ( \italic a ) } r8 f[ g f bes d,] | c[ a'16 g] bes[ a g f] c'8[ ees,] | d[ bes'16 c] a[ bes c d] ees[ d c ees] | d[ c bes c] a[ bes c d] ees d c ees] | d8. }](http://upload.wikimedia.org/score/e/w/ewi1kqw2ogri0zq1bgzmwjirx97b8v9/ewi1kqw2.png)
If we try to think of the simplest and most natural harmonies to accompany this melody, we shall obtain something like this—
Here the A natural and E flat in the second bar prove the key to be B flat; for there is no other key in which both these notes are found, unless one be a chromatic note; and there is no suggestion of chromatic harmony in the subject, which is diatonic throughout. Our last example in a major key
Beethoven. Mass in C.
requires little explanation. Though the leading note is not used, the feeling of the whole subject is decidedly that of the key of C, and not F. Compare the end of the subject with that of example (c) of § 28.
31. In a minor key we find the tonality equally clear, as will be seen from the following examples—
J. S. Bach. Wohltemperirtes Clavier, Fugue 2.
J. S. Bach. Partita in B minor.
