Key Change,Modulation in Haydn's quartet

[bilgekaana]

Can someone tell me what happens in bar 20 and so on. There is natural in c but haydn also put sharp on g so it is modulating to A major. I couldn't undertand the key change and modulation.

Haydn  Op.64 No.5 - D major.

[brogers70]

I don't see the modulation to A major there. The passage is in D major. The C natural you see is just a passing tone on the way to B natural, the third of the subdominant. The G sharp in the second violin and the E sharp in the viola are also just passing tones, not indications of a key change. They're there for color, not for modulation.

[samwitdangol]

I do not think it modulated to A major; the G# is part of the secondary dominant and the A functions as the dominant
The C-natural is simply part of the chromatic scale.

I am not an expert on this. I would greatly appreciate it if someone would correct me if I have said anything wrong.

[bilgekaana]

Thank you for your answers altough I have 1 question how is C natural a leading tone to B ?

[samwitdangol]

Thank you for your answers altough I have 1 question how is C natural a leading tone to B ?

The C-Natural is a nonharmonic tone. It is not part of the harmony and it leads/resolves into the B.

[brogers70]

Thank you for your answers altough I have 1 question how is C natural a leading tone to B ?

The C natural is not a leading tone to B.

You can think of it this way. The C natural occurs in the D7 chord which resolves to a G chord and the c natural, the seventh of D7, drops a half step to b natural, the third of G major. That is a common voicing for a D7 -> G progression. Or you can think of it as just a chromatic passing tone on the way from d to b. If you listen though, I think you'll hear it as a part of a seventh chord. Still not a modulation, though, just a little color.

Here's a link to the Wikipedia article on non-chord tones, which include passing tones such as the c natural you were wondering about. https://en.wikipedia.org/wiki/Nonchord_tone

[bilgekaana]

Thank you everyone for your helps!!!