What's happening?

[51072]

In measure 16 of the first movement of the Moonlight sonata there is, I think, a C major 7 chord, followed by a iv chord (borrowed from B minor? but then I'm not sure what the A# is). But how does this relate to the key of B major or B minor? (In measure 15 the key changes from B minor to B major very quickly it seems, but either way the C major 7 chord confuses me)

Is there another way to analyze this? Or am I missing something?

[ajspiano]

The chord is Eminor - not CM7 - though I appreciate that its a subtle difference.

The C in the melody is not really a chord tone, its creating tension and disonance against the chord just in passing.. i think so anyway, just taking a quick look.

The A# may be the raised 7th from B minor. - before moving back to B major in the next bar - I should probably look closer though to be sure of it all.

Or you're in E minor, and the A# is in passing.. or its Eminor, Bminor, E minor modulations - in this type of analysis the B major chord may be the V7 in E minor..  rather than the I in B major..

[51072]

Interesting! I see what you mean. I tend to overlook non-chord tones, as I haven't committed them all to memory just yet

Maybe it would be more accurate to say the C natural and A# are changing tones?

[ajspiano]

You get more adept at this stuff if you practice improv, or even just listening to scale tones against chords (play E minor chord EGB left hand, play entire E minor scale note by note over it RH) - so you recognise the C in the melody there as the 6th in E minor - rather than the tonic in C major.

You have to recognise the 'key' and the underlying harmony, more than just try and name the chord - because the same chords exist in multiple keys, they are then made different or recognisable within the context of their key by the more complex tones like 6ths, 9ths, 11ths etc.

example - notes DFA - d minor..   but a Bb or B in the melody will differentiate between the keys of F major/C major - where as a C# would tell you its likely D minor as the tonic chord (from a minor scale rather than a minor mode of major scale harmony)

[51072]

I think I understand what you're saying and I appreciate your advice!  : )

This piece has been quite exhausting for me (I started analyzing it thinking it would be fairly simple, but I was obviously very wrong!)

What would say about measure 56-58?

I believe it modulates very briefly to E and then returns to c# on the fourth beat of  m. 57. I don't see how the two chords in measure 58 (A F# C# D#) fit into either key though.

[ajspiano]

Without refering to the score - and looking at the notes/keys you mentioned..

A F# C# D# - rearranged like this - D# F# A C#

..looking at E major - E F# G# A B C# D# E

..now looking at the locrian mode, begins on the 7th..

D#, E, F#, G#, A, B, C#, D# - can you see that its the 1 3 5 7 from this mode?

its called a half diminished chord, or it could be noted as D#m7b5 ..you will ofcourse find them by building chords on the locrian mode of any major key, - the vii chord..  it also occurs as the ii chord in the relative minor.