Music Streaming Platforms & Mastering – 3 Guiding Concepts

[Editors Note: This blog was written by Alex Sterling, an audio engineer and music producer based in New York City. He runs a commercial studio in Manhattan called Precision Sound where he provides recording, mixing, and mastering services.]

Background:

As an audio engineer and music producer I am constantly striving to help my clients music sound the best that it can for as many listeners as possible. With music streaming services like Apple Music/iTunes Radio, Spotify, Tidal, and YouTube continuing to dominate how people consume music, making sure that the listener is getting the best possible sonic experience from these platforms is very important.

Over the last several years some new technologies have been developed and integrated into the streaming service’s playback systems called Loudness Normalization.

Loudness Normalization is the automatic process of adjusting the perceived loudness of all the songs on the service to sound approximately the same as you listen from track to track.

The idea is that the listener should not have to adjust the volume control on their playback system from song to song and therefore the listening experience is more consistent. This is generally a good and useful thing and can save you from damaging your ears if a loud song comes on right after a quiet one and you had the volume control way up.

The playback system within each streaming service has an algorithm that measures the perceived loudness of your music and adjusts its level to match a loudness target level they have established. By adjusting all the songs in the service to match this target the overall loudness experience is made more consistent as people jump between songs and artists in playlists or browsing.

If your song is louder than the target it gets turned down to match and if it is softer it is sometimes made louder with peak limiting depending on the service (Spotify only).

So how do we use this knowledge to make our music sound better?

The simple answer is that we want to master our music to take into account the loudness standards that are being used to normalize our music when streaming, and prepare a master that generally complies with these new loudness standards.

Concept 1: Master for sound quality, not maximum loudness.

If possible work with a professional Mastering Engineer who understands how to balance loudness issues along with the traditional mastering goals of tonal balance and final polish etc.

If you’re mastering your own music then try to keep this in mind while you work:

Don’t pursue absolute loudness maximization, instead pursue conscious loudness targeting.

If we master our music to be as loud as possible and use a lot of peak limiting to get the loudness level very high then we are most likely sacrificing some dynamic range, transient punch, and impact to get our music to sound loud.

The mechanism of loudness maximization intentionally reduces the dynamic range of our music so the average level can be made higher. There are benefits to this such as increasing the weight and density of a mix, but there are also negatives such as the loss of punch and an increase in distortion. It’s a fine line to walk between loud enough and too loud.

Here is where loudness normalization comes in:

If our song is mastered louder than the streaming target loudness level then our song will be gained down (by the service) as a result. If you are mastering louder than the target level then you are throwing away potential dynamic range and punch for no benefit and your song will sound smaller, less punchy, and more dynamically constrained in comparison to a song that was mastered more conservatively in regards to loudness.

If we master softer than the target level then in some cases (Spotify) the streaming service actually adds gain and peak limiting to bring up the level. This is potentially sonically adverse because we don’t know what that limiting process will do to our music. Will it sound good or not? It most likely will create some loss of punch but how much is lost will be based on what content was put in.

Some music is more sensitive to this limiting process. High dynamic range jazz or classical music with pristine acoustic instruments might be more sonically damaged than a rock band song with distorted guitars for example so the result is not entirely predictable just on loudness measurement but also on musical style.

Thankfully the main platforms other than Spotify don’t add gain and peak limiting as of this writing so they are less potentially destructive to sound quality for below target content.

Concept 2: Measure loudness using a LUFS/LKFS meter.

The different streaming services have different loudness standards and algorithms to take measurements and apply the normalization but for the most part they use the basic unit system of loudness measurement called LUFS or LKFS. This metering system allows engineers to numerically meter how loud content is and make adjustments to the dynamic range accordingly.

Being able to understand how our music masters are metering with this scale is useful to see what will happen when they are streamed on different services (i.e. will the algorithm gain them up or down to meet the target or not?)

Concept 3: Choose which loudness standard to master to.

Direct your mastering engineer if you are working with one to master to a target loudness level and consult with them about what they feel is an appropriate target level for your music. If you are mastering jazz or classical music you probably don’t want to make a very loud master for sound quality and dynamic range reasons but if you are making a heavy rock, pop, or, hip hop master that wants to be more intense then a louder target may be more suitable.

iTunes Sound Check and Apple Music/iTunes Radio use a target level of
-16LUFS and this would be a suitable target for more dynamic material.

Tidal uses a target level of -14LUFS that is a nice middle ground for most music that wants to be somewhat dynamic.

YouTube uses a target level of -13LUFS, a tiny bit less dynamic than Tidal.

Spotify uses a loudness target of -11LUFS and as you can see this is 5 dB louder than iTunes/Apple Music. This is more in the territory of low dynamic range, heavily limited content.

Somewhere in the middle of -16LUFS and -11LUFS might be the best target loudness for your music based on your desired dynamic range but the goal is not to go above the chosen target otherwise your content gets gained down on playback and dynamic range is lost.

In all services except Spotify, content that measures lower than target loudness is not gained up. So for people working with very dynamic classical music or film soundtracks those big dynamic movements will not be lost on most streaming platforms.

However since Spotify is unique and adds gain and peak limiting if your content is below target it is potentially the most destructive sonically. So should you master to -11LUFS and save your music from Spotify’s peak limiting but lose dynamic range on the other platforms? It’s a compromise that you have to decide for yourself in consultation with your mastering engineer.

You might want to test out what -11LUFS sounds like in the studio and hear what the effect of that limiting is. Is it better to master that loud yourself and compensate in other ways for the lost punch and lower dynamic range? Or should you accept that Spotify users get a different dynamic range than iTunes users and let your music be more dynamic for the rest of the platforms?

In all cases there is no benefit to going above -11 LUFS because that is the loudest target level used by any service. If you go louder than -11LUFS then your music will be turned down and dynamic range and punch will be lost on all the services needlessly and permanently.

Further Reading:

Great info – graphic on the different streaming loudness targets.

More info on LUFS/LKFS metering.