[hnlmorg]

The way it works is a producer will grab dozens of samples, then they'll loop things. Some stuff will sound good, some wont. Most of it will require a little polish (EQing etc) to tidy up. While a producer will have an ear for it to begin with (which can be a learned skill) you have to bare in mind that you only hear the samples that did sound good and none of the dozens of samples that were rejected afterwards.

Source: I used to write a few dance tracks in a past life