The pregap on a
Red Book audio CD
Compact Disc Digital Audio (CDDA or CD-DA), also known as Digital Audio Compact Disc or simply as Audio CD, is the standard format for audio compact discs. The standard is defined in the '' Red Book'' technical specifications, which is why t ...
is the portion of the audio track that precedes "
index
Index (: indexes or 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 the Halo Array in the ...
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 to ...
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 and the first of its Windows 9x family of operating systems, released to manufacturing on July 14, 1995, and generally to retail on August 24, 1995. Windows 95 merged ...
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 "CD Extra" format.
Hidden audio tracks
On certain CDs, such as ''
Light Years
A light-year, alternatively spelled light year (ly or lyr), is a unit of length used to express astronomical distances and is equal to exactly , which is approximately 9.46 trillion km or 5.88 trillion mi. As defined by the International Astro ...
'' by
Kylie Minogue
Kylie Ann Minogue (; born 28 May 1968) is an Australian singer, songwriter, and actress. Frequently referred to as the "Honorific nicknames in popular music, Princess of Pop", she has achieved recognition in both the music industry and fas ...
, ''
HoboSapiens
''HoboSapiens'' is a solo studio album by John Cale, his first album since 1996's ''Walking on Locusts''. ''HoboSapiens'' was released by EMI Records, EMI in October 2003, and was preceded by the EP ''5 Tracks'' in May 2003. A single was released ...
'' by
John Cale
John Davies Cale (born 9 March 1942) is a Welsh musician, composer, 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 styles across rock, dr ...
, or ''
Factory Showroom
''Factory Showroom'' is the sixth studio album by the American alternative rock band They Might Be Giants, released in 1996 by Elektra Records. It was the band's first album to be produced by Pat Dillett, who would go on to work with the band ...
'' by
They Might Be Giants
They Might Be Giants, often abbreviated as TMBG, is an American alternative rock and Children's music, children's band formed in 1982 by John Flansburgh and John Linnell. During TMBG's early years, Flansburgh and Linnell frequently performed as ...
, 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
Toast is an optical disc authoring and media conversion software application for macOS. 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 directly th ...
and a custom
.cue file can provide a way around this.
Ripping of pregap audio is supported by the application X Lossless Decoder.
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 for CD and DVD authoring.
The project was maintained for over two decades by Jörg Schilling, who died on October 1 ...
supports writing any kind of pregap
*
cdrdao
cdrdao (''“ CD recorder disc-at-once”'') is a free and open source utility software application for authoring and ripping of audio and data CD-ROMs. It is licensed under GPL-2.0 or Later. The application is available for several operatin ...
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 with tracks hidden in the pregap
This is a list of compact disc albums with tracks hidden in the pregap
The pregap on a Red Book audio CD is the portion of the audio track that precedes "index 01" for a given track in the table of contents (TOC). The pregap ("index 00") is ...
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, by James "Jimbo" Mathus (vocals and guitar), Tom Maxwell (vocals and guitar), Katharine Whalen (vocals, banjo, ukulele), Chris Phillips (d ...
"Hot" ECD
{{Compact disc
Audio engineering
Compact disc