I hide a smile, I guard a gasp, I dress for balls or stop a rasp. On stage I'm drama, in clinics I task. What slips on quick?

When fair and foul dost dance upon the shore, Thee find'st a force that ever waxes more. Dost mark the moon, her beckoning embrace? An unseen pull on waters' restless face.

The one to grip the seams, And shy away from beams. Though centered in the diamond light it stands, for all to see. It’s best to keep a count, Be weary when it lashes out. It starts its day in a pen of bulls, preparing to take you out.

I fit in the palm of your hand but I fill the whole room. What am I?

A house has a few but music has many. One lets you pass or even bars entry. Another differentiates between music and sound. When spelled differently the boat can be safely bound.