One of the underlying principles behind Noh Theatre and one which accounts for every movent made on stage, as well as the (almost unbearable) apparent slowness of the thing.
'Jo' is slow, 'ha' is faster, and 'kyu' is very rapid indeed, coming to an abrupt cessation of action. Every play has a 'jo ha kyu' movement, every action and footstep has one too. Noh actors, when they walk, begin moving their feet very very slowly, keeping their heel on the ground. They bring their foot up, almost to perpendicular, quite quickly, and then quickly slap it down on the floor (I'm exaggerating here to prove a point, but you get the gist).
The play itself will start slowly (veeeeery slowly), and then speed up perhaps 7/8ths of the way in. It will be very fast at the end, and stop suddenly with a stamp on the stage from the shite actor (that always makes me laugh - it's pronounced 'shtay' and is not a comment on their acting abilities).
There are 'jo' plays too - intentionally slow, 'ha' plays which are a little faster, and 'kyu' plays which are actually quite quick (quick in Noh terms, you understand - think of a tortoise on speed). The slowest Noh gets is at the 'jo' section of a 'jo' play; the fastest, the kyu of a kyu. You get the idea.
There is reasoning behind all this. The 'jo' is meant to lull the watcher, to send him into a trance like state - there are problems with this - see below. The 'ha' is meant to instil action and meaning. The 'kyu' is supposed to wake up the audience, in a revelationary manner. It is for this reason that the whole art form is infused with the 'jo ha kyu' principle.
The problem with the 'jo' phase is this. If an audience is expecting something to take a long time, then how can any sort of real, trance-inducing, slowness happen? An audience will be aware of watching for it. For this reason, the 'jo' can get really very slow indeed. The main actor will not even come out from behind the curtain at the top end of the bridge (by the third pine) until all the audience is looking in that direction, and is beginning to suspect something has gone wrong because the curtain hasn't opened. And this leads to yet more problems. An audience that knows that the actor isn't going to come on until this point will be expecting it even more. Almost self-defeating really.
Mind you, cynicism aside, the whole 'jo ha kyu' thing does actually work. Every sense, feeling and idea that an audience member does take away from Noh is revelatory and mystical. They just have to be careful not to fall asleep before the magic works.