Some songs tend to emphasize a single drop as the beginning of the high point, or climax, of the track in vocal sub-genres this occurs most in the last repetition of the chorus, while in nonvocal genres it occurs in the last quarter of the track.
Many genres of EDM have more than one drop during a track, especially if the song is built on a 'dance-pop' verse/chorus with vocals a drop may be heard somewhere during each chorus as the high point of that verse/chorus cycle.