I read somewhere that Emajor is the dominant (V) chord in A minor. Is this correct? If so, why is it not Eminor, since the A minor scale has no sharps or flats in it?
Yes it is the dominant chord. The third is sharpened to G# to make a major chord, which gives a stronger cadence when moving V-i. This is why the Harmonic Minor has a sharpened seventh degree, to create the sharpened third in the dominant chord (or leading note in the scale, whichever way you want to think about it). In common-practice harmony, the strong, major dominant chord helps define the key, so the Harmonic Minor scale, with its sharpened seventh is used. (The major V chord of the Harmonic Minor helps the harmony to function, hence the name.) However, if one is not using common-practice harmony, for instance in a lot of rock, pop, jazz and folk music, it is perfectly acceptable to use the Natural Minor, in which case chord V is minor, and the key is defined less strongly by any cadences moving from v-i.
It is correct to a certain extent. You are absolutely right that the 'natural' A minor scale has no sharps in it, and the v chord would be an E minor.
However, minor scales come in several 'flavors'. There is the natural minor, harmonic minor, and melodic minor. The harmonic minor is the same as the minor scale with the 7th raised by a semi-tone.
Ergo, the A minor harmonic scale is A,B,C,D,E,F,G#,A - which as you can see provides the G# that is present in the E major chord. The harmonic minor is quite common and thus it can be said that the dominant V (upper case is important here) chord for A minor is E major.
When people refer to a “minor scale”, they don’t always think of the natural minor scale. Quite often, they think of the harmonic minor scale, which is similar to the natural scale with the seventh degree raised by a semitone.
As the seventh degree is the third of the dominant chord, the dominant chord is major in harmonic minor scales.
For example, the A harmonic minor scale is
A B C D E F G# and the dominant chord is
E G# B, i.e. E major.
The point of any dominant chord is to lead back to the tonic chord. The best way to do this is by using the leading tone (Natural 7th in major, raised 7th in minor). Because of how the natural minor scale is formulated, the leading tone is omitted from the scale. This however does not change the fact that the leading tone gives a very strong pull to the tonic. This gave rise to the other two minor scales the other posts have alluded to.
Regardless of whether you are in major key or minor key dominant chords will contain the leading tone whether it is the 3rd of the chord (V) or the root of the chord (viio). To do this in minor the 7th must be altered and because of this alteration the parallel major and minor keys will share the same dominant chords because of how the chords are built.
So yes E major is a dominant chord of A minor.
It's probably more often the V because it has that G#. That comes from both the harmonic and the melodic minors. Sometimes Eminor is the V and it is used in lots of songs.Yes, it originates from the natural minor (or in some cases the melodic). It isn't so decisive, but still pushes towards I, which is the job of any V chord.
The notes of the dominant chord of a minor is E/G#/B. E - G# is a Major third while E - B is a perfect fifth. This makes the chord Major.
I think you are getting confused by what it means for a scale to minor / Major and what it means for a chord to minor / Major.
A Major Chord is one with a Major third and a perfect fifth. This can happen in both minor and Major keys and is not fixed to what key you are in.
E7 is the Dominant of A minor. E major is almost correct but, you are missing the minor 7. The major third and the minor 7 of every dominant chord make the interval of a tritone.
The major key has two dominant chords: V (G) and vii (Bdim). Both of these are dominant to the Cmajor chord (tonic) and also have a dominant function to the A minor chord which is also a tonic chord and contains the same chord tones as a C6.
Additionally, there are secondary dominant chords, these are found outside the key. The secondary dominant for the A minor chord is Emajor.
A natural minor scale has these notes:
A, B, C, D, E, F, G
Therefore the A natural minor has this chord progression:
I - Am II - Bdim III - C IV - Dm V - Em VI - F VII- G
However for an A harmonic minor scale which has these notes:
A, B, C, D, E, F, G#
has this chord progression:
I - Am II - Bdim III - C#5 IV - Dm V - E VI - F VII - G#dim
Although in many cases they would prefer this chord progression:
I - Am II - Bdim III - C#5 IV - Dm V - E7 VI - F VII - G#dim