The pregap on a
Red Book audio CD is the portion of the audio track that precedes "
index
Index (or its plural form indices) may refer to:
Arts, entertainment, and media Fictional entities
* Index (''A Certain Magical Index''), a character in the light novel series ''A Certain Magical Index''
* The Index, an item on a Halo megastru ...
01" for a given track in the table of contents (TOC). The pregap ("index 00") is typically two seconds long and usually, but not always, contains silence. Popular uses for having the pregap contain audio are live CDs, track interludes, and
hidden song
In the field of recorded music, a hidden track (sometimes called a ghost track, secret track or unlisted track) is a song or a piece of audio that has been placed on a CD, audio cassette, LP record, or other recorded medium, in such a way as t ...
s in the pregap of the first track (detailed below).
Unconventional uses of the pregap
Computer data in pregap
The track 01 pregap was used to hide computer data, allowing computers to detect a data track whereas conventional CD players would continue to see the CD as an audio CD.
This method was made obsolete in mid 1996 when an update to
Windows 95
Windows 95 is a consumer-oriented operating system developed by Microsoft as part of its Windows 9x family of operating systems. The first operating system in the 9x family, it is the successor to Windows 3.1x, and was released to manufacturin ...
in driver
SCSI1HLP.VXD
made the pregap track inaccessible. It is unclear whether this change in Microsoft Windows' behavior was intentional: for instance, it may have been intended to steer developers away from the pregap method and encourage what became the
Blue Book specification
The Blue Book is a compact disc standard developed in 1995 by Philips and Sony. It defines the Enhanced Music CD format (E-CD, also known as CD-Extra, CD-Plus and CD+), which combines audio tracks and data tracks on the same disc. The format was ...
"CD Extra" format.
Hidden audio tracks
On certain CDs, such as ''
Light Years
A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...
'' by
Kylie Minogue
Kylie Ann Minogue (; born 28 May 1968) is an Australian singer, songwriter and actress. She is the highest-selling female Australian artist of all time, having sold over 80 million records worldwide. She has been recognised for reinve ...
, ''
HoboSapiens
''HoboSapiens'' is a solo studio album by John Cale, his first album since 1996's '' Walking on Locusts''. ''HoboSapiens'' was released by EMI in October 2003, and was preceded by the EP '' 5 Tracks'' in May 2003. A single was released for "Thin ...
'' by
John Cale
John Davies Cale (born 9 March 1942) is a Welsh musician, composer, singer, songwriter and record producer who was a founding member of the American rock band the Velvet Underground. Over his six-decade career, Cale has worked in various styl ...
, or ''
Factory Showroom
''Factory Showroom'' is the sixth studio album by the American rock band They Might Be Giants. It was released in 1996 by Elektra Records.
The album reclaims the more diverse and electronic sound of their early work, but differed from previous ...
'' by
They Might Be Giants
They Might Be Giants (often abbreviated as TMBG) is an American alternative rock band formed in 1982 by John Flansburgh and John Linnell. During TMBG's early years, Flansburgh and Linnell frequently performed as a duo, often accompanied by a d ...
, the pregap before track 1 contains a
hidden track
In the field of recorded music, a hidden track (sometimes called a ghost track, secret track or unlisted track) is a song or a piece of audio that has been placed on a CD, audio cassette, LP record, or other recorded medium, in such a way as t ...
. The track is truly hidden in the sense that most conventional standalone players and software CD players will not see it.
Such hidden tracks can be played by playing the first song and "rewinding" (more accurately, seeking in reverse) until the actual start of the whole CD audio track.
Not all CD drives can properly extract such hidden tracks. Some drives will report errors when reading these tracks, and some will seem to extract them properly, but the extracted file will contain only silence.
Other CDs contain additional audio information in the pre-gap area of other tracks, resulting in the audio only being heard on a conventional CD player if the CD is allowed to "play through," but not if you jump to the next track.
Some CDs also contain phantom tracks consisting of ''only'' index 0 data, meaning the track can only be played on a conventional CD player by allowing the CD to play through a previous track to the next track.
Pregaps in CD-R media
OS support
Mac OS X:
Currently does not support more than a 2-second pre-gap in the first track under
its CD burning utilities. Using a combination of
Roxio Toast
Roxio Toast is an optical disc authoring and media conversion software application for Mac OS X. Its name is a play on the word ''burn'', a term used for the writing of information onto a disc through the use of a laser.
Discs can be burned di ...
and a custom
.cue file can provide a way around this.
Ripping of pregap audio is supported by the application X Lossless Decoder.
[{{Cite web, url=http://tmkk.pv.land.to/xld/index_e.html, title=X Lossless Decoder: Lossless audio decoder for Mac OS X]
Windows:
*
Exact Audio Copy
Exact Audio Copy (EAC) is a CD ripping program for Microsoft Windows. The program has been developed by Andre Wiethoff since 1998. Wiethoff's motivation for creating the program was that other such software only performed jitter correction whil ...
provides the functionality to write to Index 0
Linux:
*
cdrecord
cdrtools (formerly known as cdrecord) is a collection of independent projects of free software/ open source computer programs.
The project was maintained for over two decades by Jörg Schilling, who died on October 10, 2021.
Because of some ...
supports writing any kind of pregap
*
cdrdao
cdrdao (''“CD recorder disc-at-once”'') is a free utility software product for authoring and ripping of CD-ROMs. The program is released under the GPL. Cdrdao records audio or data CD-Rs in disk-at-once mode based on a textual description ...
supports writing any kind of pregap
*
K3B, a frontend for several CD/DVD burning/ripping utilities, supports hiding the first track in the pregap of the second one.
See also
*
List of albums containing a hidden track
This article contains a list of the names of albums that contain a hidden track and also information on how to find them. Not all printings of an album contain the same track arrangements, so some copies of a particular album may not have the hi ...
Notes
External links
Technical Specificationsof the
Squirrel Nut Zippers
Squirrel Nut Zippers is an American swing and jazz band formed in 1993 in Chapel Hill, North Carolina, Chapel Hill, North Carolina, by Jimbo Mathus, James "Jimbo" Mathus (vocals and guitar), Tom Maxwell (singer), Tom Maxwell (vocals and guitar), ...
"Hot" ECD
Audio engineering
Compact disc