Interval question

[yyz]

Hey everybody, I just got a theory book and according to one of the examples in the book an F and a B are a perfect 4th. I've been playing music all my life and if I'm correct, I think that's wrong. That would be a diminished 5th, right? Could someone please elaborate? Thanks a lot.

[Kelly Coyle]

Originally Posted by yyz

Hey everybody, I just got a theory book and according to one of the examples in the book an F and a B are a perfect 4th. I've been playing music all my life and if I'm correct, I think that's wrong. That would be a diminished 5th, right? Could someone please elaborate? Thanks a lot.

Yup it's wrong. Yer cool. (You could call that interval an augmented fourth if you needed it to be a fourth. Or a tritone.)

[yyz]

Damn book. I think they meant to put a flat in front of the B. Good book despite that though.

[Tash]

Or an F#

[djcruse]

Originally Posted by yyz

Hey everybody, I just got a theory book and according to one of the examples in the book an F and a B are a perfect 4th. I've been playing music all my life and if I'm correct, I think that's wrong. That would be a diminished 5th, right? Could someone please elaborate? Thanks a lot.

It wouldn't be a diminished fifth. In this case it would be an augmented fourth. Your ear hears them the same, but in terms of notation they are different.

Why? The interval from F to B (provided they are in the same octave) is always some sort of fourth. Perfect, diminished, augmented, etc., - always a fourth. F to C would be a fifth.

But from what you describe it just sounds like a typo.