Unresolved secondary leading tone · Rules
In a secondary dominant (V/V, V7/IV…), its leading tone rises by semitone to its tonic, just like the leading tone of the key. It may fall chromatically in the same voice (V7/V → V7).
- Unresolved secondary leading tone: In a secondary dominant (V/V, V7/IV…), its leading tone rises by semitone to its tonic, just like the leading tone of the key. It may fall chromatically in the same voice (V7/V → V7). (Piston, ch. 16, pp. 251 and 253)