Dynamic Range in Music

Dynamic range in music is the span between the softest and loudest sounds in a recording, measured in decibels. It is what separates a whispered verse from a full chorus, and a drum hit from the room around it. There are two scales. Macro-dynamics are the large-scale contour of a song: verses quieter than choruses, a breakdown before a drop. Micro-dynamics are the note-to-note changes: the attack of a snare against its decay, a picked note against a strummed chord. Heavy compression and limiting reduce both, which is why an over-limited master can sound loud but flat. Dynamic range is not the same as loudness. Two masters can have the same integrated loudness and very different dynamics; one reaches its loudness with steady density, the other with contrast between quiet and loud passages.

Several meters describe level and dynamics, and they answer different questions. Peak meters protect against clipping; loudness meters describe how loud a track feels; range measures describe how much the level moves.

Loudness normalization adjusts playback volume so tracks play at a similar perceived loudness, whatever level they were mastered at. Spotify documents its behaviour in detail: the default setting (Normal) plays tracks at -14 LUFS, and Premium listeners can choose Loud (-11 LUFS) or Quiet (-19 LUFS). Spotify measures loudness when you upload and adjusts volume at playback; it does not change your file. A master louder than the target is turned down (negative gain), with no added distortion. A quieter master is turned up (positive gain), but Spotify considers the track's headroom and leaves 1 dB of headroom for lossy encodings. Whole albums are normalized together so the level differences between their tracks survive; tracks are adjusted individually when shuffled or mixed with other albums. For masters, Spotify recommends -14 LUFS integrated with true peak below -1 dBTP, and true peak below -2 dBTP if the master is louder than -14 LUFS, to avoid extra distortion when the track is encoded to a lossy format.

The loudness war was the trend, from the 1990s through the 2000s, of mastering records ever louder with heavy compression and limiting, because louder masters stood out on radio and in side-by-side comparisons. The cost was dynamic range and, at the extreme, audible distortion. Metallica's Death Magnetic (2008) became the best-known example: listeners compared the heavily limited CD master with the separately mastered version made for the Guitar Hero game, which kept far more dynamics, and many preferred the game version. Loudness normalization on streaming services removed most of the incentive. A master pushed far above the target is turned down to the same playback loudness as everything else, so it keeps the side effects of heavy limiting (flatter transients, less contrast) without the extra loudness.

A compressor reduces the level of a signal once it passes a threshold, by a ratio: at 4:1, a signal 4 dB over the threshold comes out 1 dB over. Make-up gain then raises the whole signal, so the result is louder on average with less difference between quiet and loud moments. Compression is a normal mixing tool. Gentle settings add consistency and punch to vocals, bass and drum buses. Sidechain compression, where one signal (often the kick) controls the compressor on another (often a bass or pad), creates the pumping effect common in dance music. A limiter is a compressor with a very high ratio and fast response that stops the signal passing a ceiling. It is the last processor in most masters. Pushing more gain into a limiter raises loudness and lowers PLR and LRA; it is also where true peaks above the ceiling can appear if the limiter works on samples rather than the reconstructed waveform, which is why true-peak limiting and metering exist.

Measure three numbers before you send a master to your distributor: integrated loudness, true peak and loudness range. Integrated loudness tells you how much a platform will turn the track up or down. On Spotify, a master at -9 LUFS plays about 5 dB quieter than it was mastered; a master at -17 LUFS is turned up about 3 dB if its true peak leaves room. Neither is wrong, but it helps to know which will happen. True peak tells you whether encoding may clip. Spotify's guidance is below -1 dBTP, and below -2 dBTP for masters louder than -14 LUFS. Loudness range and PLR tell you whether the loudness came at the cost of contrast. There is no universal right value; compare with references in your genre.