I asked my theory teacher why it is bad, but he said because you don't and i said why like six times and he said, "because if you do bad things will happen." What bad things? I wonder if this is how to summon the devil.......
I am the only sane person on the planet. Does that make me crazy?

Crank the Mids
Doubling the leading tone just sounds like shit. Kind of like parallel 5ths and octaves. Its not that you CANT. Its just that, for the very specific type of composing your doing, it sounds bad.

The devil can only be summoned by tritones.

Also, vi6 chords help.
Last edited by tubatom868686 at Dec 23, 2009,
to above. Angels can be summoned by tritones. They are the most holey and un-changeable thing I can think of...

Anyway, it is just a 'rule' developed in classical music.

As above said, it was developed the same time parallel fifths were outlawed :P

Nowadays you'll find you here it quite a bit. Sometimes the rule stands true and it doesn't sound great, but you can do it and make it sound good.

He's teaching you the standard exam type theory which is totally fair enough! Just be aware when these types of things come up.. these rules were made a long long long time ago and times change. This stuff doesn't apply so much anymore, but if you don't obey them in an exam or assessment situation prepare for a bad grade.
There are two reasons to avoid doubling of the leading tone:

First, since the leading tone has a strong pull toward the tonic, you would have parallel octaves when resolving it. If you try to avoid them by moving one of the voices in contrary motion, your resolution won't sound that satisfying.

Second, the leading tone is the most unstable scale degree and doubling it gives more roughness to the sound.
Kenam is right. There was something I forgot to mention.

If you double the leading tone, your putting your self into a situation where you have to break another rule as well. You either have to have parallel octaves, or an unresolved leading tone
Quote by tenfold
What does it mean to double the leading tone?

most of the time in four part writing, you write music in 4 voices, tenor, alto, soprano, and bass. if you use a triad, you normally double the root *not always, but mostly* if you double the leading tone, it means you use the leading tone of the scale in two of the voices
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Quote by tenfold
What does it mean to double the leading tone?

When you have a V-I/i Cadence in four part harmony you don't double the leading note.

Double the root or 5th (it's advised to double the root).

Other instances of doubling:

In root position chords double the bass note or the 5th.

In first inversion chords double any note apart from the bass note when the distance between the 5th and root above it is a perfect 4th. If the interval is an augmented 4th then double the bass note.

In second inversion chords double the bass note.