Why is it so easy to tell the difference between live and recorded music?

Not in all cases so easy. But the answer is obvious - because microphones cannot 'hear' everything that ear can. Not to mention what happens to the signal down the chain.

The difference is primarily dynamic range.

DR yes (although there are easily available recordings with DRs of 20, or even better, of real music, and when I play them I still know they are recordings), but other things as well, such as ambient cues.

But most things your want to listen to aren't.

Sometimes my Dachshund is fooled by animal sounds on various albums, and occasionally a solo vocal that comes in, but mostly she just looks at me and lets me know she's not fooled, it's still just a stereo...

Tom

In spite of my dog, I still prefer listening to my system than listening to almost any live event, (the exception being the symphony). 

Tom

I was told a dachshund can bring down a 160 lb man who’s had a twenty foot head start.

Hahaha!!!

She IS fast...

Mostly because your brain is telling you there's no way it could be live music when the eyes transmit to it an image of speakers. Place musicians on a stage pretending to play while a pair of speakers behind them actually play, then it gets more difficult to tell the difference.

When I played "Jazz Wolf" CD, even on a very low-end mini system, my dog would Always join all those other wolfies "out there"! It was fun!!
Better hearing or not, personal involvement must have played a role. Music or sounds coming from TV never fooled him

I was fooled by my stereo more than once: when listening to Roger Water's "Amused to Death" I always thought that its a neighbors dog barking outside. It was recorded thru some Q-Sound effects, but as mentioned already by @gs5556, my expectations fooled me. The effect is lost thru the headphones. 

Aside from the fact is the listener usually knows beforehand if what they are listening to is live or not, it’s not always so easy assuming a good setup and good recording to go with it. There are often many clues in a studio recording that will give it away as not being live but not always.

Dynamic range certainly plays a huge role.

I also notice the ability of many a system to start and stop fails to mirror reality, even as some claim the superiority of their means of implementation.

But for me, I'm MOST bothered by the incorrect tone / timbre of most high-end audio systems, even when they possess notable dynamic range or speed.  There's simply an unnatural sonic signature to most high-end audio components / systems I encounter.  I cannot get past that

Some of Frank Zappa's stuff is very hard to tell if it is live or not. Mostly very well done.

Frank Zappa’s entire catalogue or most of it has one outstanding characteristic. Dynamic range. The Official Dynamic Range Database. Check it out.

I posted about this a while ago.  To my ears, there is very rarely a doubt.  Sight unseen, approaching an area where music is being played, without prior knowledge, I can very reliably tell if "it's live or if it's Memorex";-)

I've always thought that, on a subconscious level, your brain goes down its "survival checklist" when it encounters new sounds. One of the questions it asks: Is what I'm hearing able to cause physical harm? Is it real? Is it close? Etc. A marching band passing your open window leaves no doubt as to its potential for physical harm. Any stereo you are likely hear just won't have the same cues.   

I’m in the same boat as Trelja , natural tone and timbre seem the limiting factor for many systems/components. This is the bottleneck more so than dynamic range which is the next most limiting factor IMHO. The addition of a certain hardness or "edge" signature just labels the sound artificial or canned more often than not. These are the two main culprits but there’re others that exist.
Charles

If you mean live music that is amplified like rock music, then the live sound you hear may be from the PA system which gives it a very forward, often one dimensional sound. Also the reverberation may affect the sound (many greatful dead recordings suffer from this). When audiophiles say live music is the ideal I often disagree unless they are referring to classical or chamber or choir music. I enjoy rock and blues concerts but find that many concerts have pretty bad sound due to the location (eg basketball arenas) but also because everything is pipped through the pa loudspeakers which to me often loses the separation and texture. When I played in a band I loved hearing the drums and fender amp directly when we rehearsed. Going the the PA system usually degrades the sound unless great care is taken by the performers and crew. 

Back in the 1960s AR marketed their AR3a loudspeakers with a live vs. recording demonstration.  A string ensemble, solo violinist or guitarist would play a piece and at some point the sound would be switched to a recording.  Listeners would then be asked to comment whether they could tell when the switch took place.  The majority of listeners could not accurately detect the switch over.  A key element of the demonstration was the special way the recordings were made.  They were made either outdoors or in anechoic chamber to avoid the "double acoustic space signature" effect during playback.

onhwy61, I've heard of similar demonstration (long time ago) with symphony orchestra and the best audio system available behind the curtain.  Herber Von Karajan, asked to participate, detected system with ease every time. When they asked him how different it sounded to him he said that record player was slowing down slightly during orchestra's forte.   Surprisingly famous musicians with such perfect hearing often don't care about the sound.

Not at all easy with large ATC to recognize the difference between live and a good recording. I think wide even dispersion and high dynamic range and a neutral uncolored sounding speaker are major factors but there is a lot that is required - so it is rare enough that I understand why many folks might think it would be impossible.

I have followed Steve for years and I think his technical knowledge is outstanding but his hearing preferences are towards colored hi-fi style sound. Nothing wrong with his tastes but you arent ever going to find realistic audio reproduction with those kind of preferences.

Limitless frequency and dynamic swings

I guess I should explain why wide even sound dispersion is critical. Maybe Steve will read this and learn something.

Our ears and brain are very good at integrating sound with the environment. A speaker that radiates evenly throughout the entire spectrum is like a conventional light bulb - it lights up the room evenly. A speaker that varies in radiation with frequency will give telltale signs to our ears - just like a spotlight produces a beam that is in one direction. When you couple sound with an environment like a room or space - again our ears instantly pick up on directional variations in sound and a spotlight or narrow beam over some frequencies is instantly recognizable even from the differences in reverberation from sound coming out a room window!!!

It is very similar to cupping hands over your mouth when speaking or using a megaphone to increase the directionality of the voice - we can hear this change in reverberant sound instantly.

So our ears brain are able to work out very quickly and easily that a beam of sound is NOT natural sounding. Only wide even dispersion sounds natural as it will evenly reflect off of the space around the sound source and the listener.

We are so good at this that standing in an acoustically treated totally dead room can make people feel sick - as the eyes and ears do not correlate what is seen with what is heard.

This is why horn speakers with uneven dispersion and a higher degree of directionality never sound natural except in a very small sweetspot and a nearfield seating position (this minimizes the uneven reverberation that makes it obvious that the sound is artificial).

AR chose small ensembles or solo instruments for their tests.  A symphony orchestra would be a far more challenging.

I don't think it's always easy to tell the difference since there have been specific occasions where I've been fooled, but in general, live sound reacts with background noises in a different manner than amplified music.  It floats above it as opposed to cutting through it.  Sorry for the obscure language.

I would have to say that audio gear is so good at this point that I am 99% happy with recordings sitting on my comfortable chair in my living room which has decent (although not perfect) acoustics.
I have difficulty EVER recalling hearing great sound at a live concert, although the experience alone was well worth the trouble of going in the 1st place.  When s great performer comes out on stage, whether it's Frank Zappa or the LSO, i get goosebumps anyway.  But for truly balanced sound and no coughing or other distractions, i can now die a happy person. Only ballet or opera, (or Woodstock) requires a ticket and a good seat (imho).  If you can get a string quartet to come over to your house and play, that (of course) would be terrific also...

...."Live v. Not...."

Dynamics, yes...but as an 'omni fan'....Ambiance....MHO, obviously...

...as soon as you move....(Generally*....)....*poof*...

( * = ...unless you've been very careful and/or very lucky to have the 'disposable income' to 'attend to the details'....in whatever manner or fashion you felt compelled to....Again, IMHO....)

I totally agree with everything Trelja notes particularly tone/ timbre, it's always been and continues to be so obvious to me. I find it remarkable how good recorded can get considering all the challenges posed. To me what is most important is conveying the emotion in the performance.

My wife and I attended a middle-school grandchild's band concert last night. Dynamics/tone/timbre. Especially dynamics. Amazing really. Reminded me how inadequate my system is in comparison. Reality check. Sigh...

Tom

Tom, have you heard a Direct-To-Disk LP played by a Decca/London cartridge? That's the closest to live I've heard. Very dynamic, and "immediate".

Have not, but have read wonderful things about the D2D LPs, and about that cartridge. Very special...