What is it?
Why is it desirable?
In its most basic of forms, dynamic range is the difference between the quietest and loudest discernible sound in a piece of music, at a given point in time.
Dynamic range measurements of a piece of music are most often presented in either PLR or PSR measurements. The difference here being that PSR is a short-term measurement and PLR will usually be throughout an entire a song or album.
PSR is equal to the true peak value subtracted by the short term average loudness over a given 3 second period.
PLR is the long term average meaning it is equal to the true peak value subtracted by the integrated loudness throughout the course a full song or album.
So why is it desirable? Dynamic range is desirable for a vast number of reasons. There's no doubt that a healthy dynamic range can create powerful and transparent sounding music, however, it does have to be used in the right way. Reasons for this will be discussed in further articles. Many mastering engineers such as Ian Shepherd, Bob Ludwig and Bob Katz are pioneers of dynamic range and consider it one of the most powerful tools at their disposal and this is for good reason. Ian Shepherd started Dynamic Range Day to raise awareness of the loudness war and both Ludwig and Katz have featured as part of it on several occasions. It began in 2011 and every year sees a 'Dynamic Range Day Award' winner, which is an album considered to exhibit exceptional use of dynamic range. Productions Ludwig worked on have won 5 times over the past 10 years.
It's hard to define a simple answer as to why it is desirable, though the testimony of so many of these critically acclaimed engineers has to stand for something. The following articles hope to prove why in my opinion, as a general rule, more dynamic range is desirable.