Food. Some foods you can't eat just one of. Some foods whet your appetite, making you want more of them. You can then maintain that appetite by indulging occasionally. The appetite can only be extinguished by gorging yourself on them.
Chocolate. Potato chips.
Similarly in drama, the brief appearance of an interesting character or possibility whets interest. Examples include a bad guy or love interest, or a super-power. Interest can be maintained through brief appearances, then satisfied in a final showdown. Examples: The Darth characters in star wars, River's super-powers in Firefly, uber-badguys in Buffy, Bester in Babylon 5.
This is a scale-free phenomenon. For example, in a drama series, interest in a character can be maintained for an episode if they appear at a certain rate, or for a series if they appear at a certain slightly lesser rate.
Similarly in music. The statement of the tonic, or of a melodic theme, whets the appetite for its repetition. Music ends when the tonic is stated with sufficient force that we are satiated, and when all themes have been sufficiently repeated.
This again is scale-free. One may have a tonic note or melodic phrase occur through an entire piece or just a section. Tonic notes or phrases need to be used sparingly through a piece in order to maintain one's appetite for them. This allows for pieces of music that are are diverse but form a coherent whole.
Why do people put themselves through all this teasing? On purpose? Frankly, it all seems a little kinky.
17/6/2006: Ok, so here (mp3) is a little whetting of the appetite stuff going on. Self reference. No real satiety, just that basic drive for variety, and definitely no teasing yet.