So the song is in the key of E and the fifth tone of that scale is B so it should be major, right? However the song starts with Em chord and instead of B, Bm sounds better (flat 7th?), what am I missing here?
Hello and welcome to the community.
If the song has an Em chord it is not in the key of E (E major).
It could be in the key of E minor. And Bm is a chord in that key.
What is the song? What are the other chords / the progression?
You’re song is either in the Key of Em or G.
Must have been typing when Richard replied
If there’s an Em and Bm in the song and if we assume the chord progression is diatonic, the options are the following:
Em is degree I, Bm is degree V: key of G major / E minor
Em is degree II, Bm is degree VI: key of D major / B minor
Em is degree i, Bm is degree v: E minor
Em is degree vi, Bm is iii degree : key of G major
Em is degree II, Bm is degree VI: key of D major
Bm is degree i and Em is degree iv: key of B minor
Even thou Major and Relative minor Keys have the same notes they are not the same Key and it’s a bad habit to get into thinking they are.
E F# A
E Bm
E Bm
E C
E C
D That’s all the chords used in the song. So even if I use the minor scale from E, the fifth note is B, right? So in a major scale 1st chord is major, 2-3 minor and so on - but what changes in minor? Do all chords in a scale get a flat 3rd or something?
In order for a B chord to become a Bm chord, it can’t have a flat 3rd, so it has to get a flat 7th?
Whether the song is in major or minor key is determined by ear only or is there some trick to it?
Do you mean the difference it makes like in a I-IV-V progression: G-C-D vs Em-Am-Bm ? I think I get now.
As @stitch stitch mentioned above, major keys have relative minor keys which have the same chords. You can get the relative minor key by starting on degree VI of the given major scale. E.g. the relative minor of the C major scale will be the A minor scale. It has the same chords as the C major scale but starting from Am.
The 7ths (major, minor, dominant, flat, etc) are chord extensions and they are very much present in major keys as well.
The chord progression of this song is simply not fully diatonic. Nothing wrong with that, it happens quite often. The progression you have can be written in the key of G major as:
VI maj-VII maj-II maj
VI maj-III
VI maj-III
VI maj-IV
VI maj-IV
V
Or in E major:
I-II maj-IV
I-V min
I-V min
I-bVI maj (flat sixth)
I-bVI maj
bVII maj
In the key of D major:
II maj-III maj-V
II maj-VI
II maj-VI
II maj-bVII maj (bVII degree, not a minor 7th chord)
II maj-bVII maj
I
This looks like straightforward f# to me.
The 5th chord (C here) is often played as a major or dominant in minor keys.
Am I learning @Richard_close2u? 
Wouldn’t that be in the key of F rather than F#? 
The key of F# has 6 #s the chord progression only has 1
There is no F# in the Key of F.
What song is it? My guess is there is a Key change or borrowed Chords.
My mistake- I didn’t notice it was an F# Major chord in the sequence. I suppose that could be a ‘borrowed’ chord, but would that make sense if it was the key itself? I’ve got a feeling someone’s going to have to tidy this thread a bit after my ‘contribution’ 
1 Like
Hi Rick, I know.
I wrote f# (minor) not F# (major). All the other chords fit in the f# (minor) key
You wrote it starts with Em up above but now write E.
5 major chords and 1 minor?
If that is right then it is not a diatonic progression there are out-of-key chords.
Sorry, my mistake, it starts with an E chord. Looks like I’ve confused myself and everyone else haha.
Right, so looks like this progression is in the key of E? And as far as I understand the fifth triad in a major scale is B chord, but it becomes Bm here?
E major scale:
E, F#, G#, A, B, C#, D#
Diatonic chords of the key of E major:
E, F#m, G#m, A, B, C#m, D#dim
Your chord progression:
E, F#, ___, A Bm, C, __
Only two of those chords (E and A) are in the key of E.
Options.
The Bm and the C chords are found in the key of E minor. They ckuld be viewed as borrowed chords. F# is not in the key of E minor though, in that key the F# is a diminished chord.
The F# chord could be borrowed from the E Lydian (chord borrowing from a mode or modal interchange).
Something about that works theoretically but is a bit clunky.
It is late and I need to park my response for the night.
What song is this?
@Wolfaz Alex why don’t you do everyone a favour and tell us what song it is. Maybe the tabs you’re using are wrong.
Does it just sound better to your ears? Is the song using a B or a Bm?
You are getting a little confused with mention of flat 7th. Flat 7th does not determine if a chord is major or minor. That is determined solely by the third degree.
No, major = 3rd, minor = b3rd, diminished = b3rd and b5th.
In order for a B chord to become Bm there is only one way to do it - which is to take the 3rd of the major chord and flatten it to make a minor chord.
It is determined by the overall sound, what feels like home, and the surrounding chords.
THere is a 'trick# to it and you need to understand theory to use and apply it.
If C is the 5th chord, it is the key of F, yes. But It is not the key of F either.
When you write that it 'become Bm’ what do you mean? What is making it become Bm. Has it changed from B major at some other point in the song?
I think any further discussion is going to be futile until we know the song and the full, accurate progression from start to finish.
Cheers
Richard
I would also add, along with the song title the source of the progression(s) you have stated so far. There are a lot of bad transcriptions on the web.
The song is Bonnie Pink - It’s Gonna Rain
Chords are from here ITS GONNA RAIN CHORDS by BONNIE PINK @ Ultimate-Guitar.Com