The practice of focusing on loudness in mastering can be traced back to the introduction of the compact disc itself but also existed to some extent when vinyl was the primary released recording medium and when 7" singles were played on jukebox machines in clubs and bars. Jukeboxes were oftensettoapre-determinedlevelbyPatek Philippe watches the bar owner, yet any record that was mastered "hotter" than the others before or after it would gain the attention of the crowd. The song would stand out. Many record companies would print compilation records, and when artists and producers found their song was quieter than others on the compilation, they would insist that their song be remastered to be competitive. Also, many Motown records pushed the limits of how loud records could be made, and record labels there were "notorious for cutting some of the hottest 45s in the industry."[2] However, because of the limitations of the vinyl format, loudness and compression on a released recording were restricted in order to make the physical medium playablerestrictions which do not exist on digital media such as CDsand as a result, increasing loudness levels never reached the significance that they have in the CD era.[3] In addition, modern computer-based digital audio effects processing allows mastering engineers to have greater control over the loudness of a song; for example, it gives them the ability to use a "brick wall" limiter which limits the volume level of an audio signal with no delay (hardware equivalents have a short delay caused by processing time).[4]
The stages of the CDs loudness increase are often split over the two-and-a-half decades of the medium's existence. Since CDs were not the primary medium for popular music until the tail end of the 1980s, there was little motivation for competitive loudness practices then. CD players were also very expensive and thus commonly exclusive to high-end systems that would show the shortcomings of higher recording levels.
As a result, the common practice of mastering music involved matching the highest peak of a recording at, or close to, digital full scale, and referring to digital levels along the lines of more familiar analog VU meters. When using VU meters, a certain point (usually -14 dBFS, or about 20% of the disc's amplitude on a linear scale) was used in the same way as the saturation point (signified as 0 dB) of analog recording, with several dB of the CD's recording level reserved for amplitude exceeding the saturation point (often referred to as the "red zone", signified by a red bar in the meter display), because digital media cannot exceed 0 dB. The average level of the average rock song during most of the decade was around -18 dBFS.[citation needed]
At the turn of the decade, CDs with music louder than this level began to surface, and CD volumes became more and more likely to exceed the digital limit as long as such amplification would not involve clipping more than approximately two to four digital samples, resulting in recordings where the peaks on an average rock or beat-heavy pop CD hovered near (usually in the range of -3 dB) 0 dB but only occasionally reached it. The Guns N' Roses album Appetite for Destruction from 1987 is an early example of this, with levels averaging -15 dB for all the tracks.[5]
In the early 1990s, some mastering engineers decided to take this a step further and treat the music's levels exactly as they would the levels of an analog tape and equate digital full scale with the analog saturation point, with the recording just loud enough so that each (or almost every) beat would peak at or close to 0 dBFS. Though there were some early cases (such as Metallica's Black Album in 1991), albums mastered in this fashion generally did not appear until 1992. Dirt by Alice In Chains and Faith No More's Angel Dust are some examples from this year. The loudness of releases during this period varied greatly depending on the philosophies of the engineer and others involved in the mastering process. This style of "hot" mastering became commonplace in 1994, though exceptions, such as the album Superunknown by Soundgarden from the same year, still existed. The most common loudness for a rock release in terms of average power was around -12 dBFS. Overall, most rock and pop music released in the 1990s followed this method to a certain extent.[citation needed]
The concept of making music releases "hotter" began to appeal to people within the industry, in part because of how noticeably louder releases had become and also in part to the notion that customers preferred louder sounding CDs.[citation needed] Engineers, musicians and labels each developed their own ideas of how CDs could be made louder.[citation needed] In 1994, the digital brickwall limiter with look-ahead (to pull down peak levels before they happened) was first mass-produced. While the increase in CD loudness was gradual throughout the 1990s, some opted to push the format to the limit, such as on Oasis's widely popular album (What's the Story) Morning Glory?, which averaged -8 dBFS on many of its tracksa rare occurrence, especially in the year it was released (1995). In 1997, Iggy Pop assisted in the remix and remaster of the 1973 album Raw Power by his former band The Stooges, creating an album that, to this day, is arguably the loudest rock CD ever recorded. It has an average of -4 dBFS in places.[5]
Loud mastering practices caught media attention in 2008 with the release of Metallica's Death Magnetic album. The CD version of the recording has a high average loudness that pushes peaks beyond the point of digital clipping, resulting in distortion. These findings were reported by customers and music industry professionals. These findings were later covered in multiple international publications, including Rolling Stone,[6] The Wall Street Journal,[7] BBC Radio,[8] Wired,[9] and The Guardian.[10] Ted Jensen, a mastering engineer involved in the Death Magnetic recordings, subsequently criticized the approach employed during the production process.[11] A version of the release without dynamic range compression was included in the downloadable content for Guitar Hero III.[12]
The standards of loudness would reach their limit in the 2000s. -10 dB had been the standard for the past several years, but this was often pushed to -9 dB. However, -6 to -5 dBFS is common in rock, contemporary R&B, pop, and hip hop music. Quieter exceptions to today's standards are rare. The releases of 2008 reached average levels as high as -3 dBFS, such as Angels & Airwaves' I-Empire, which yields almost 30 times the loudness of a THX standard recording (-20 dBFS). However, in late 2008, mastering engineer Bob Ludwig offered three versions of the Guns N' Roses album Chinese Democracy for approval to co-producers Axl Rose and Caram Costanzo, and they selected the one with the least compression. Ludwig wrote, "I was floored when I heard theydecidedtogowithmyfulldynamicsomega watch version and the loudness-for-loudness-sake versions be damned."[13] Ludwig feels that the "fan and press backlash against the recent heavily compressed recordings finally set the context for someone to take a stand and return to putting music and dynamics above sheer level."[13]