Dr. B Music Theory - Dr. B Music Theory Lesson 40 (Modulation 101)

TOPICS: 0:00 - Modulation 1:16 - Modulation vs. Tonicization 2:47 - Key relationships 9:40 - Common Chord Modulation 12:46 - Analyzing Common Chord Modulation QUESTION IN COMMENTS andrewnorris1 Hello Dr. B., Here is a question which confuses me, but I felt sure you would know the answer. I am using the wonderful book, Tonal Harmony by Kostka, I think you know it. There is a modulation exercise on page 296 with an extract of Bach: Jesu, du bist mein. The key signature has 2 flats yet it states the key as c minor and the modulation to E flat occurs at bar 5. When you put the Roman numerals under the chords it makes sense, the first chord as a i (c minor tonic). I then went to Youtube to find a recording of it and someone has made a very colourful analysis but entirely in E flat and the first and final chords are listed as vi, submediant. Firstly, is this a mistake? Secondly, what is the reason for writing one key signature when the opening and concluding chords suggest a different one. Thanks in advance for any light you can shed on this. All the best, Andrew The video answer is here: https://youtu.be/TO5-oDNw7QA