EQing an audio file with a digital processor

How to Master a Song: Key Concepts

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If you are looking to release music professionally, it’s important to know how the whole process works. One step that newcomers to record production often aren’t familiar with is audio mastering. What is audio mastering? Mastering is the application of EQ and compression to a finished mix to optimize playback across all systems and formats.

In the old days, the audio mastering process was done to make sure every songs played at the same level for the radio so the DJ wouldn’t have to adjust the volume. For all the science involved, music mastering is an art, and those who do it as a profession are highly skilled; in general, it’s not recommended to master a project yourself. But it is good to be educated about the process so you know what to expect and know the importance of and key concepts in mastering.

The role of mastering in music production

For those new to the recording process, it has four basic stages: recording, mixing, mastering, and manufacturing (if you’re making physical product). Since mastering is the last step before manufacturing and distribution, it is vital to make sure that your music sounds the way you want it to at this step.

Often, good mastering can make or break a recording. Many of the best mastering engineers command large fees and are famous in their own right, like Bernie Grundman, Greg Calbi, Scott Hull, and Emily Lazar, to name a few.

Basic mastering concepts

The goal of mastering is to “polish” the song so that it is even in volume and audio consistency, making it able to fit in seamlessly on the radio, on playlists, and on an album. This makes it easier for the listener to connect with the music emotionally as audio disruptions such as volume spikes are evened out. Keep in mind that, when mastering, you are applying changes to the entire mix of a song as a whole and not individual tracks; changing the sound of individual tracks is done during mixing.

Mastering engineers use EQ, compression, and limiting to accomplish this goal. Engineers differ on the order of applying EQ/compression/limiting, but there isn’t a right or wrong way to do this. In general, applying EQ adjustments before compression makes for a warmer, fuller sound and using EQ after the compressor creates a cleaner, clearer sound. Ultimately it is about you and the mastering engineer achieving the sound you are envisioning in your head.

Preparing for mastering music

Learning key concepts in mastering is crucial for knowing how to finalize a mix to prepare it for this step. Most engineers will provide you with a list of specifications for your files so you can be prepared and not waste time and money.

If your mixes are digital, your source mixes should be in an uncompressed format like WAV or AIFF; mastering from a compressed format like MP3 or WMA will not sound good. Also, your mixes should have about 3-4 decibels of headroom to avoid clipping and distortion on the final mix and to give the mastering engineer room to work with.

Most mastering houses recommend not applying compression and limiting to your tracks during mixing as it can interfere with the headroom the mastering engineer needs. When in doubt, defer to your mastering house and be clear on what they need when finishing your final mixes.

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How mastering works, step by step

Here is an overview of a general mastering process for a single song. This is not intended as a guide to DIY mastering; we highly recommend budgeting for a professional mastering engineer. This might even be one of the key concepts of mastering: It’s best to not do it yourself!

Step 1: Listening and analyzing

To begin, your mastering engineer will listen intently to your track, noting volume dynamics, balance between bass and treble, and other points. They’ll identify areas where there might be problems they have to address. Many of them also use a spectrum analyzer to see more clearly the “hot” and “cold” frequency areas of the song.

Step 2: Equalization (EQ)

The principle of “less is more” is one of the key concepts of mastering, but maybe most of all in the EQ department. A good mastering engineer will lightly apply EQ adjustments to portions of the song that require it. There may be problem areas that require small cuts in frequency and perhaps a wide curve might be carefully applied to boost or cut a certain frequency range. But there may be little need for EQ at all if the mix has been balanced well.

Step 3: Compression and limiting

Compression makes your mix louder and reduces the dynamic range so that loud sounds are softer and soft sounds are louder. Limiting sets a cap on how high your volume can go while enhancing “perceived loudness” and is an effective tool to reduce the risk of distortion or clipping. Your mastering engineer will apply these as necessary on your song.

Different compressors add their own specific sonic footprint, so you’ll want to make sure that the ones being used by your engineer add to the sound the way you want them to. Overuse of compression sounds terrible, but a top-notch mastering engineer knows when to walk away and will only use what is absolutely necessary.

Step 4: Enhancing stereo width

Stereo width refers to the size of the acoustic image (also known as studio field) created by stereo speakers. Mixing engineers position sounds within the stereo field; panning tracks outwards makes the mix sound wider and positioning tracks in the center of the field will make the mix sound narrow. Almost all issues of stereo width can and should be addressed in the mixing process where you can pan individual tracks. However, sometimes during mixing, errors are made or issues of width are not noticed. In these instances, stereo width can be added during mastering to make the mix sound wider. But again, the principle of “less is more” is key: too much width added in mastering can cause phasing issues.

Step 5: Finalizing with dithering and exporting

Once all the above adjustments have been made and you and your engineer are happy with your mastered song, then it is time to apply a dither and export your final master. Dithering is the process of adding noise to a signal to reduce quantization distortion that occurs when reducing the bit depth of a file. So, if you are mixing and mastering in 24-bit audio or higher, it’s crucial to apply a dither when bouncing final masters to 16-bit audio. Your engineer will be familiar with the intricacies of dithering and will also need to know the file specs to export your masters to for manufacturing if you intend to press physical product like CDs and vinyl LPs.

DIY mastering vs. professional mastering

If you are hell-bent on attempting to master your own recordings, there are websites and software plug-ins available encouraging you in the DIY direction. But we don’t recommend this. You want your music to stand out from the herd and one of the best ways to do that is professional mastering. Mastering is an art; a great mastering engineer can apply magic to your music. That’s why even professional studios typically outsource the mastering process to a mastering studio.

The SoundLAB at Disc Makers has been in business for over 20 years and offers high quality CD and vinyl mastering at affordable prices. They have a wide selection of analog and digital gear, can handle masters from WAV files to analog tape reels, and are priced to meet the budget of independent musicians.

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Chris Huff

About Chris Huff

Chris Huff has been a professional singer, multi-instrumentalist, songwriter, and producer for over 25 years. He has worked as a sideman with Peter Yarrow (Peter, Paul, and Mary), Echo and the Bunnymen, Chuck Hammer (David Bowie, Lou Reed), and Tom Kitt (Broadway composer of Next To Normal). Chris also wrote liner notes for David Bowie’s Live And Well CD, and his full-length album, 'bout Time is available on iTunes.

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