Tango music is not like other dance music. Most dancing is done to music with a fixed rhythmic pattern. That pattern sets the temporal framework to build your movement on, and interest in the dance is created by changing how you fit your movement to the framework or how you work that framework. Since the rhythm is fixed, the choice of what steps to make is fairly free at any given point in the dance. You know exactly when the next important beat will be.
Tango music's great innovation is its irregular rhythmic structure. You may have a habeñero beat for two bars, followed by a simple 4/4 for two bars, then a period of 3-3-2 rhythm finished off with a quick blast of 2/4. Without knowing the exact arrangement being played, you are never sure just what will happen next. Now, you may be thinking that a lot of music is like that, but you are probably thinking of the melody. Focus on the accompaniment and you'll almost always find a stable rhythm underpinning the melodic rhythmic variation. With tangos, the accompaniment varies as much as the melody, and varies separately, to boot.
So the challenge of tango dancing is to hear that variation, to build your movement not on a fixed, stable, predictable pattern, but on a shifting, organic environment. Now, obviously, there are many tango dancers out there that don't really pay attention to the rhythmic variation, who plod along stepping on the 1 and the 3, regardless of whether the instruments are actually playing anything at the time. These people are beginners. However many years they have been dancing, however fancy the leg flicks and linear boleos they pull are, they are still at heart beginners. The experienced tango dancers are listening to the music, and letting it pull them. They may move to the melody some times, and the accompaniment at others. Perhaps the leader is moving to one while the follower moves to the other. This is where the magic lies. This is the secret of the so-called tangasm; moving with the music as the music changes. It's the complex synchronicity that really grabs the human psyche.
This is what makes tango difficult, and what makes tango wonderful. It's also why so many tango dancers and DJs keep returning to the same recordings from well over half a century ago. It's not that the "Golden Era" tango musicians where in some way better than all recent musicians. The best certainly were pretty damn good - there was a lot of competition, and enough money being made in tango music for some serious professionalism to develop. I'm sure there were some other factors that time and distance make it difficult to assess. But that level of unpredictability also makes a lot of tango dancers crave familiarity in the music. If you are deeply familiar with a complex piece of music, you can build towards that complex synchronicity. You know when the piece switches to 3-3-2, you know where the runs and pauses are. And so with that knowledge, with that familiarity, you can reach that "tangasm" level synchronicity.
Or can you?
Is it really the full experience, or a simulacrum? From my personal experience as a tango leader, it's pretty good, but I think the times when I really feel it is when I am dancing to something I've never heard before, or even a familiar tune by a new band, and the music does something I don't expect, something interesting - and I catch it. I stop just so after a quick run exactly when the music comes to one of those big drawn out chords on the bandoneón. It's a heck of a rush, and it's why I'll always dance to live music.