Topic: Moonlight Sonata. 1st Movement. Key changes?

[jessetr]

Hi,

As I learn music theory, I know that Moonlight is in C# minor. 

But as I test that, and play just C#, at some point during the 1st movement the C# suddenly sounds off key for a while.  If you need the spot where it goes awry, I will find the measure.  But I was hoping that all you experts would know the spot already.   

Does the piece change key?  It doesn't indicate it anywhere on the sheet music.  What is going on exactly?  Please feel free to use technical language.

Thank you!

[(poco) Sforzando]

There are several places in the first movement where the music modulates (changes key) from C# minor. One is measure 23, where the music cadences in F# minor (the subdominant key). The subdominant is somewhat unusual for reasons too complicated to go into, but changes of key are standard for virtually any piece of music. They are not necessarily indicated by changes in key signature; instead accidentals (sharps, flats, naturals) will inform the performer or reader of the music that a different key is temporarily in place.

Hi,

As I learn music theory, I know that Moonlight is in C# minor. 

But as I test that, and play just C#, at some point during the 1st movement the C# suddenly sounds off key for a while.  If you need the spot where it goes awry, I will find the measure.  But I was hoping that all you experts would know the spot already.   

Does the piece change key?  It doesn't indicate it anywhere on the sheet music.  What is going on exactly?  Please feel free to use technical language.

Thank you!

[Holden]

The music is changing key all the time as well as moving between the minor and the major. For example the first two bars are technically in C# minor and then changes in bar three to A for half a bar before moving to D/F# in bar 4, G#7 in bar 5 then back to C#minor again in bar 6. If you Google it, you should be able to find sheet music that will show you those key changes.

[(poco) Sforzando]

The music is changing key all the time as well as moving between the minor and the major. For example the first two bars are technically in C# minor and then changes in bar three to A for half a bar before moving to D/F# in bar 4, G#7 in bar 5 then back to C#minor again in bar 6. If you Google it, you should be able to find sheet music that will show you those key changes.

I'm going to disagree with you. The A major chord in 3 is the submediant (scale degree 6) in C# minor. The music has not changed key at this point. The D/F# is flat degree 2, or what's known as a Neapolitan 6th. It takes more than a chord to establish a key change. The first modulation in the piece starts in bar 7 and establishes the relative major (E major) in bar 9. But rather unusually, instead of closing the exposiiton in E major, Beethoven diverts to F# minor at 23.

[jessetr]

Well, damn!!

 

[Holden]

I'm going to disagree with you. The A major chord in 3 is the submediant (scale degree 5) in C# minor. The music has not changed key at this point. The D/F# is flat degree 2, or what's known as a Neapolitan 6th. It takes more than a chord to establish a key change. The first modulation in the piece starts in bar 7 and establishes the relative major (E major) in bar 9. But rather unusually, instead of closing the exposiiton in E major, Beethoven diverts to F# minor at 23.

I'll bow to your much better knowledge of musical theory - mine's very rusty obviously.

[(poco) Sforzando]

I'll bow to your much better knowledge of musical theory - mine's very rusty obviously.

I corrected a typo in my original post above: submediant is scale degree 6, not 5.

[jessetr]

What are the key changes for bars 23 - 46?

[Dry Brett Kavanaugh]

I'm going to disagree with you. The A major chord in 3 is the submediant (scale degree 6) in C# minor. The music has not changed key at this point.

You maybe right but this is not necessarily the case, I tend to see. The Amaj could possibly be a tonic chord in a changed key of Amaj. Your interpretation is valid only if the Amaj here is placed as a subdominant to Emaj (submediant to C#min). Again, your interpretation maybe right, but we must see the score.  if D note is raised, you are right. If D is not raised, it may indicate a key change to Amaj.

[(poco) Sforzando]

You maybe right but this is not necessarily the case, I tend to see. The Amaj could possibly be a tonic chord in a changed key of Amaj. Your interpretation is valid only if the Amaj here is placed as a subdominant to Emaj (submediant to C#min). Again, your interpretation maybe right, but we must see the score.  if D note is raised, you are right. If D is not raised, it may indicate a key change to Amaj.

No key changes in the first 7 bars; these are all in the tonic key of C# minor. The A chord is the submediant, the D chord in first inversion (where the note D is flattened from D#) is a Neapolitan sixth.

[(poco) Sforzando]

What are the key changes for bars 23 - 46?

19-23 is a modulation to the subdominant key of F# minor, with 23 giving us the tonic of that key in root position. 25 begins moving back to C# minor, with the G# in the bass 28-39 being what's called a dominant preparation towards re-establishing the main key. 42 begins the recapitulation in the home key. 42-46 again modulate to E major as in the exposition, but from 49 the music remains in the home key.

There are a lot of subtleties that can't be addressed in a casual Internet post, but if you can find Charles Rosen's "Beethoven's Piano Sonatas: A Short Companion," you'll get a very thorough (albeit highly technical) analysis.

[Dry Brett Kavanaugh]

No key changes in the first 7 bars; these are all in the tonic key of C# minor. The A chord is the submediant, the D chord in first inversion (where the note D is flattened from D#) is a Neapolitan sixth.

Sounds good. Thank you for the response!