E A major second is equivalent to a whole note, or two semitones, and two semitones down from G-flat (which is enharmonically equivalent to F-sharp) is E, although it might be written as F-flat depending on the key signature. F-flat, E to G-flat would be a diminished 3rd, not a major second..
The answer to this question is not always simple, however if you want a definite answer, look at the tips below: If you wanted to end on a perfect cadence, you should modulate to a G major chord and then move down to the tonic chord (C major). If you wanted to end on a plagal cadence, you would modulate up a fourth to a F major chord and then resolve on a C major chord. If you wanted to end on am imperfect cadence you simply modulate to the dominant chord (in this case G major) and end there. Finally, if you wanted to end on an interrupted cadence you modulate from the tonic chord (C major) to the relative minor, an A minor chord. So in most cases a song which began in C major should end in the tonic key (C major), however a song in C major can end in G major (an imperfect cadence) or in A minor (an interrupted cadence). Hope this helps.
The circle of fifths is a way of figuring out how many sharps/flats a key. Starting with C major, you go up a fifth and put a sharp on the seventh degree of the scale, which is F sharp - so the key of G major has one sharp. This can be done by going up a fifth from G to D, in D major the F sharp (third degree) is already present and again you add a sharp to the seventh note, C-sharp, thus D major has two sharps. This goes all the way round to C-sharp major, with all notes made sharp. You go down a fifth from C major to F major and lower the fourth degree, making the B a B flat, this F major has one flat. Again by going down a fifth from F is B flat and the fourth note is lowered so you lower the E to E flat, so B flat major has two flats. You keep going until you reach the key of C flat major, with all notes in the scale flat.
E Major - E, G#, B. B Major - B, D#, F#. C# Minor - C#, E, G#. A Major - A, C#, E.
Ab major
The 2nd in C major is D.
A minor second.
E-flat
D natural
The supertonic of any scale is the second degree of the scale. Therefore, the supertonic of C major is D.
The interval between C and D is a major second or a "whole step".
There are two tetrachords in a diatonic scale. The second tetrachord has the higher four notes. In D major, they are A B C# and D.
The easiest way to modulate from G to F major is by modulating down to C major on the way. In that way you are moving down the circle of fourths/fifths.
You can have a musical scale starting anywhere you like. On the piano, the simplest scale is C major, in which the second note is D. In all major and minor scales, you can find the second note by moving up two semitones from the first note (C-C#-D or G-G#-A)
Throughout the whole keyboard, there are a few sets of "A's" and "C's" and so on. If you are starting from middle C and then the A above it, obviously A is higher. If you are starting from middle C and then going down for the A below it, the C is obviously higher.
Which composer? Mozart's concerto no. 23 in A has its second theme in E major, and in the recapitulation it returns in A major. Schumann's concerto in A minor has its second theme in C major, returning in A major for the recapitulation.
Transpose the music down a major second.