Show off your theory chops with my weekly challenge! You’ll find a new question here every Monday. Please comment to post your reply.
This week’s challenge:
This is from J. S. Bach’s Toccata and Fugue in D minor. What type of cadence is highlighted in red?

Listen to the Audio
ANSWER for 6/7/21
This is a Phrygian Cadence, or Phrygian Half Cadence. Most often seen in minor keys, we go from a iv chord in first inversion to V (Gm/Bb to A). Notice that the bass drops down a half-step, which is reminiscent of the first two notes in the Phrygian mode (hence the cadence’s name).

You can brush up on your cadences with all new lessons in the Diatonic Harmony Course! Sign up for a monthly subscription for full access to all video lessons, worksheets, and answer keys. Also, this year I’ll be adding new lessons on modes. I created Breaking Barlines with one thing in mind: making music theory effective and FUN!
It’s a bit tricky, but I believe it’s a Plagal Cadence.
The first part in red is telling us something with the C#, but we need more information.
The second part in red also has the C#, but in the bass clef there’s two Bb’s and a D in the treble clef. So that’s clearly the IV chord: Bb Maj. This is pointing to the Plagal Cadence. Notice that we never actually see the V chord anywhere.
We then end in the bass clef with A and E. Combine that with the C# up top and we have A Maj. This is more or less a substitution for the tonic.
Thank you for taking the weekly challenge! Actually, in both red sections we have the complete iv and V chords. Careful on the second red section: the first chord is G minor, not Bb major. I think you might have believed this passage was in F major, but it’s D minor. Good effort, but this isn’t a plagal cadence. The plagal cadence is iv–i. This cadence ends on V, and it’s approached by iv6. It’s a type of half cadence, and there’s a special name for it 🙂
Phrygian half cadence
I agree
A wise choice, my master!
Jackpot! Well done; you can also simply call it the Phrygian Cadence.
Half cadence: iv to V in D minor.
Correct! And Phrygian was his name-O!