A short discourse about Loudness by phat suspekt
In January 2021 Spotify changed it's normalization method from ReplayGain to ITU 1770 to give the customer a better listening experience. This change makes it obsolete to upload a highly compressed master and go for maximum loudness. Too much loudness will result in a lack of dynamics.
All streaming services, including Spotify and Youtube, demand an average loudness level of about -14 LUFS to -16 LUFS (Loudness Units relative to Full Scale). Songs with a higher or lower loudness level will get normalized. These -14 LUFS to -16 LUFS are not the specifications for the final master of your song though. Find a level that serves the music best and works in the interest of the song or album.
An integrated level of about -12 LUFS, with peaks not higher than -1 dBTP, and a max short-term level of not more than -10 or -8 LUFS is a reasonable starting point for uploading to all the major streaming platforms.
You can check your loudness levels here: https://www.loudnesspenalty.com/
ClUB and CD Masters
Most masters for mainstream rap music (Trap, Drill, Classic Hiphop) are compressed and limited heavily to accomplish a loud master. The average loudness of rap songs for club play and CD sits somewhere between -9 LUFS and -6 LUFS .
The reason for this is that a louder master sounds better to most listeners, and the high compression rate results in a powerful sound and upfront instrumentation.
The specific loudness of the final master also depends on the genre and the purpose of the master. A trap banger will have a higher loudness level than a jazzy boombap track in most cases.
The process of giving a song density and punch starts in the mixing stage, with sidechaining, parallel bus compression, equalizers and many other tools. You have to use a decent amount of compression and limiting to achieve the loudness of a -8 LUFS master.
The job of the mastering engineer is to create a loud and sonically competitive master without losing the dynamics of the song and the clearness of the mix. This can be done by using several steps of slight compression and multiband limiting, M/S processing and use of dynamic equalizers.
Learn more about mixing and mastering on the mixing page.