Let it be noticed that this subject might have been considered as in the key of B flat throughout; it would then have taken a real answer. Kirnberger has preferred to regard it as in F until the last two bars. The tonal change might have been made after the B flat in the fifth bar; but this would have altered the form of the subject needlessly. The point, to illustrate which this passage is quoted, is the treatment of the A in the penultimate bar. It is first regarded as third of dominant, and answered by D, and then looked at as leading note of B flat, and answered by E natural. We saw in § 88 how two notes in the subject were answered by the same note; here is the converse—the same note in the subject has two different notes in the answer.
136. The answering of one note by two is sometimes to be met with in the case of the dominant and supertonic, as in the following passage—
Here the supertonic at (a) is first answered by the supertonic of E, and then treated as dominant of E, and answered by dominant of A. Evidently had it been so regarded the first time, it would have utterly spoilt the answer.
137. Sometimes the dominant is answered first by tonic and then by supertonic, even when there is no modulation.
