What Is a PQ Sheet?

A PQ sheet provides important information for CD duplicators.

Any audio compact disc that is duplicated professionally must conform to the technical specifications outlined in the Red Book -- an industry standard originally created by Philips and Sony in the 1980s -- so that it can be played on any CD player. Red Book CDs are typically accompanied by a document known as a PQ sheet, which contains information about the identity and duration of each audio track.

Importance

Essentially, a PQ sheet provides all the information that a professional duplicating company needs to duplicate a CD without unnecessarily transferring the content back and forth between media, which results in a loss of audio quality. The information on the PQ sheet is checked by a mastering engineer during the first and most important stage of CD duplication known as “glass mastering.”

Reference Points

During mastering, reference points known as P and Q codes are added to the beginning and end of each audio track. P codes indicate to a CD player where audio tracks start and end, while Q codes provide a table of contents, including the identity and duration of each track. Collectively, P and Q codes provide the information you see -- the number of tracks, their lengths and the total length of the CD -- when you load a CD into a CD player. A PQ sheet is thus named because it lists the P and Q codes contained in the CD data, among other information.

Q Code Data

Q code data includes International Standard Recording Code (ISRC) numbers, which uniquely identify each audio track recorded on a CD. Q code data also includes several other types of data, such as a 13-digit bar code known as a media catalog number and a copy-prohibit flag, which indicates whether or not digital recorders can copy the content of the CD.

ISRC Number

ISRC numbers are used mainly to allow royalties to be paid automatically to a collection agency -- such as the American Society of Composers, Authors and Publishers or Broadcast Music Incorporated -- when an audio track is played on a radio station. ISRC numbers consist of a two-character country code, a registrant code, the last two digits of the year in which the code was issued and a unique five-digit number. They are issued by the ISRC Agency in the United States on a track-by-track basis.

References

• What is Music Production; Russ Hepworth-Sawyer, et al.
• About Audio Mastering Software: What is a Red Book CD?