youre right

5 and 17 are also ok (sub dominant)

Yes. Fifths can give a slight tense feel to the patch.

I figured i would add to this to help out a little...+5 on the virus is in semitones which is what makes an interval major or minor...this does not make it a Fifth...if u actually look at the keyboard and start from C; +1 is C#/Db, +2 is D, +3 is D#/Eb, +4 is E/Fb, +5 is F/E#...now if u r playin in C major...and u count up 5 semitones, which is F and then cound the note letters it is not a fifth rather it is a fourth...and on top of that it is a perfect fourth because a fourth can can not be major or minor...it can be augmented or diminished...

So a quick review...to get the interval u count the letter names of the keys in your scale...to get whether it is major minor perfect augmented or diminished u count the semitones....

peace
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