The search uses the title of the set list item which can be changed to whatever you like in the Set List Manager, which gives you more control over what is being searched for. The screen shot below shows the results of changing the name of a set list item to "You" from "Donna Lee" resulting in music player search results containing the word "You" in the song title.
Once you select a track from the list of tracks, play back begins, to stop play back, press the play icon again. To pause the track you must use the music player app since there is no functionality included in iGigBook to pause the track.