Leading tone

Hi
how to write a seventh leading tone chord for 4 part harmony for strings?.
Thank you

I'm not an expert on this, so someone can correct me if I have this wrong, but in any Dominant 7th to Tonic cadence (V7 - I), or even just Dominant Triad to tonic, the third of the dominant chord is a leading 7th to the tonic. For example, in C major, a G7 or G resolving to C has a B as the third of the G chord and the seventh tone of the key signature rising a half step to the Tonic C.

Is this what you mean?

So in four part harmony you could have

D - F -G - B going to C - E - G - C

You could also put a B in the bass instead of D to double the leading tone movement.

You need to be more clear. Are you asking about a leading tone triad, (a 3 note chord which contains the 7th scale note i.e., the leading tone) or are you asking about a leading tone 7th chord, which is a leading tone triad plus a 7th from the root?

In the key of C major:

Leading tone triad = B diminished = notes BDF. It's almost always found in first inversion, i.e., D F B or D B F. And as it's 4 part harmony, one note must be doubled, which for this chord must be D, the 3rd. That's because B needs to rise to C so if you double B - you'll have parallel octaves. Same applies to F, which needs to fall to E in standard 4 part harmony final cadence points.

Leading tone 7th chord = B^ø7 half diminished 7th = B D F A (also known as Bm7b5). No doubling required as you already have 4 notes.