There is a lot of talk about LUFS and very often it is very unclear what is actually being talked about. LUFS numbers are being handed out without proper explanation what this actually means. Let's dive in and find some answers.
Mastering is the final step in making your song sound the best it can and create the best listening experience for your audience. Mastering is also contextual and usually involves more than a single song. It is easy to look at some (random) numbers when mastering, but the most important element of mastering are your ears: Rely on your ears, use reference tracks to do A/B testing (to compare your track with a good sounding track similar to yours) and make decisions based on that. Then measure and look at the numbers and adjust if needed. Do as little as possible to get the best results, but do whatever is needed.
Mastering engineer Ian Shepherd runs one of the best audio podcasts in my opinion sharing his insight and experience. In one of his recent shows Ian talks about the different types of LUFS tackling some of the confusion when we hear people talk about LUFS and give recommendations. The problem is it is rarely suggested what type of LUFS we are talking about. Is it Momentary LUFS, Short Term LUFS or Long Term (Integrated) LUFS?
Momentary Value - Reacts very quickly, helpful to judge loudness of speech
Short Term - 3 sec average value (similar to RMS meters). Useful to judge loudness between segments of a song (internal dynamic)
Long Term - Overall (integrated) value of a complete song (or a clip). This is what the streaming services use when deciding if values should be turned up or down.
Distribution Loudness for on-demand music service (streaming) is somewhere in the range of -14 LUFS (Spotify) to -16db (Apple Music). That DOES NOT mean that your song output has to be -14 LUFS. If you are mastering a song or an album, focus on how it sounds rather than the numbers. If a song is -9db LUFS, it will simply be "turned down" 5db when streamed on platforms such as Spotify. If your song is -16 db LUFS, it will be turned up. Keep in mind, streaming services Spotify and Apple will adjust those levels only if a song is a part of a playlist or if you´re listening in shuffle mode. If you are listening to an album, streaming services will maintain the loudness difference between songs on the album, the way it was produced, mixed and mastered.
Albums are created with the listening experience in mind and sometimes some songs are supposed to be louder than others.. Stating that everything should be mastered at a certain level is both misleading and an over-simplification.. Mastering is contextual and whatever we do should serve the song, not some random numbers handed out by random people on the internet.