Key of E Minor

[aragonzafra1950]

I'm studying the E minor primary chords,  and don't understand the V7 chord progression.  If it is a B7,why does it have only two sharps, D and F.  I guess I just don't understand this progression.

[liszt1022]

B7 only has two sharps, D# and F#. The A is natural. It's kind of hard to explain why, it's best just to know that when you make a dominant 7 chord, you make a major triad (B D# F#) and add a minor 7th (A.)

If you understand the above, great.
I'm about to type way too much, feel free to stop reading here.

1. Start with the key of E major. The V7 chord is built on the following scale degrees: 5, 7, 2, and 4.
B D# F# A.
There is no A# in the B7 here because it's built using only scale degrees found in the key of E major.

2. Minor keys use the same spelling for dominant 7ths (V7)s as their parallel-major scale. So the key of E minor uses the same V7, again with no A#.

3.You may know E minor from its key signature: one sharp. But there's another way to spell out E minor, it's called using the "harmonic" minor scale, and it goes: E F# G A B C D# E. This way, the V7 is still using notes found within the scale.

Q: What makes A better than A# in a B7 chord?
A: In a B7 chord, the A is the seventh. When you play the next chord (E major or E minor) that A falls down to G# (if E major) or G (if E minor.) Falling from A# to G is too far for it to sound right.

[nyiregyhazi]

B7 only has two sharps, D# and F#. The A is natural. It's kind of hard to explain why, it's best just to know that when you make a dominant 7 chord, you make a major triad (B D# F#) and add a minor 7th (A.)

If you understand the above, great.
I'm about to type way too much, feel free to stop reading here.

1. Start with the key of E major. The V7 chord is built on the following scale degrees: 5, 7, 2, and 4.
B D# F# A.
There is no A# in the B7 here because it's built using only scale degrees found in the key of E major.

2. Minor keys use the same spelling for dominant 7ths (V7)s as their parallel-major scale. So the key of E minor uses the same V7, again with no A#.

3.You may know E minor from its key signature: one sharp. But there's another way to spell out E minor, it's called using the "harmonic" minor scale, and it goes: E F# G A B C D# E. This way, the V7 is still using notes found within the scale.

Q: What makes A better than A# in a B7 chord?
A: In a B7 chord, the A is the seventh. When you play the next chord (E major or E minor) that A falls down to G# (if E major) or G (if E minor.) Falling from A# to G is too far for it to sound right.

It can be kept a lot simpler that that- it's just because B7 is the dominant in the key of E minor. So it has F sharp from the key signature and D sharp from the traditional raised 7th. An A sharp would have nothing do with E minor.