bII7 roman degree
The tritone substitution — the Neapolitan dominant with a 7th that SLIDES chromatically down a half step to I. It replaces V by sharing its tritone.
Where it lives
1semitones from the tonic
Major mode
dominant 7th
Hear it in context: Tritone Substitution Turnaround
Piano sound loads on first tap. Resolved in the key of C — every chord links to its full analysis.