The audio before a track’s official start
A CD’s track map can include a short lead-in before each track’s main audio. The main section is marked Index 01; the preceding section is called Index 00, or the pregap. Most of the time, that space is silent. But a disc can place music there, before the player considers Track 1 to have begun.
That makes the song awkward to find through an ordinary track-by-track search: the player’s track display may still say Track 1, even though the audio is technically before its start. Holding Rewind while Track 1 is playing can move the laser backward into that earlier section. Depending on the player, the display may show a negative time or behave in another unusual way.
A bonus that rewards curious playback
The trick worked because a CD’s track list was not a complete map of every sound on the disc. A listener could see where Track 1 began without seeing what came just before it. Artists and labels could use that hidden stretch for an extra song or other audio, turning a technical quirk into an Easter egg—a surprise tucked away for listeners who explored beyond the obvious controls.
The catch was discoverability: listeners needed the right player behavior and a hint, or enough curiosity to try rewinding. So the bonus was not simply an extra track at the end of the album. It occupied a sliver of audio the disc’s normal navigation treated as the space before the music started.
