fully diminished or half diminished in a Major scale with sevenths?

[Bob]

I need a quick brush up on my theory. 

The more I've thought it... I think I've answered my question here.


If you add sevenths to triad in a major scale, what type of seventh is the leading tone chord -- a fully diminished or half diminished seventh?  viio  or vii/o?

It's fully diminished right?  Even though that doesn't fit in with the diatonic scale, it's still altered.  Right?

[Bob]

I vaguely remember my theory prof saying it was viio, fully dim.  And possibly he said it could go either way.

Just playing up and down the Major scale with sevenths though... I think it sounds better with the half-dim version that way.  That's playing seventh in root position.  Maybe it's the Ab to C jump at the end, from viio to I, that sounds weird to me. 

[schartmanovich]

Bob,

You can use either viio or vii half-diminished in a major key; the former is more in the style of classical music. If you wish to write a viio chord in major you must flatten the 6th scale degree.