What exactly is textural density??

The more I consider the question, the more I like @oregonpapa's example of a cello or upright bass played with a bow. My sister played cello, and I've played with a couple of acoustic basses, so I'm pretty familiar with the sound they produce. The catgut strings on a bow, pulled across the strings of a cello or bass (or violin, for that matter; I've also performed with a couple of fiddle players) produces a very physical sound ( a "scraping"-type sound), one possessing lots of texture (think of running your hand across a deep pile carpet, or a loose-knit sweater ;-) .

Textural density relates to the amount of the "physical" sound of an instrument or voice, as in not just the sound a drum produces, but also the sound of the wood or plastic tip of a drumstick striking the drumhead. The friction between the stick and head creates a sound of it's own, a textural detail. Direct-to-disk LP's are superior in their ability to reveal such texture. Textural density is the opposite of "whispiness", which is the lack of physical "presence". A ghostly apparition, without physicality.

^^^

 BDP24 is correct. Textural density, when it comes to music really has to do with the individual instruments. It is that ultimate realism that we are all after ... or should be after with our audio systems. If your system is resolute enough, you can hear it in vocal cords, bowed strings, struck vibraphones ... and even notes as they are being bent by an expert harmonica player. You know it when you hear it.

Frank

This is precisely what is called "instrument timbre", each instrument playing the same note giving his own specific "textural density"....

Instrument timbre perception is  one of the most important factor to analyse to reveal the accuracy of an audio system....    

It has to do with the music composition itself not the reproduction of it nor the playing,. This reviewer blabbering about textural density through headphones doesn't know what he's talking about.

“Realism” has everything to do with the correct expression of the naturally occurring harmonics (overtones) in the timbre of musical instruments. Audio equipment does not discriminate. If a piece of audio gear does not correctly reproduce the natural tonal (textural) density of a cello (to use bdp’s example) it will, likewise, not express the natural tonal density of an upright bass playing in the same range as a cello. They may each have different harmonic signatures overall, but any deviation from “realism” in a particular frequency range will impact another instrument playing in that range to one degree or another. Mahgister speaks to this Re “timbre”.

Djones, I agree with you, but I will give the reviewer the benefit of the doubt. “Tonal density” is a better term to describe what I think he is trying to say. Musicians use this term when discussing “timbre”.