I have heard a lot of really good music and a lot of really bad stuff too! But some of the bad stuff is "technically" really good... What do I mean by this? I mean people can hit all the right notes, have a great melody, great lyrics, great production,... and still the song does nothing, it doesn't move me, it doesn't stir an emotion, it doesn't transmit anything. 9 times out of 10, it's because the performances are coming from the brain instead of the heart.
Playing from the brain means the performance has been too focused on singing the song correctly, pronouncing the words perfectly, playing precisely, and in the process the performer's personality is lost. Personality and emotion can also get lost in the editing stage and from bad direction given in the studio.
I guess you could call playing "from the heart" the auditory factor X if you are listening to a song without seeing the performance. A song that is sung from the heart and is performed with emotion hits you, it connects. It's funny because I remember taking a studio recording class and dealing with midi. You could get everything so perfectly in time that it would sound robotic, there would be no push, no pull. So, to solve this problem you could use the "humanizer" effect, and what would this do? It would make everything slightly off, not quite so perfect, create push and pull, some tension and release, make it breathe a little.
When you think about how the recording process started, there was no way of perfecting things... "fixing things up in the mix" didn't exist. In fact, there was no full drum set as everyone recorded in the same room and the drums would have overpowered the other performers. Jump ahead in time to Sgt. Pepper's Lonely Heart Club Band and you are in the era of multi-tracking and the art of studio magic. People are creating music that would be impossible to play live... It happens all the time today, you get bands showing up to a gig with backing tracks just so they can pull off the record... What worries me is that there are musicians recording albums that not only they cannot perform live, but that have never performed on a stage to a live audience prior to recording... I believe in the approach that you test your songs out on stage and get the crowd's reaction, that you "own" the song before you record it and that you have an audience waiting to receive it!
In today's industry, you need to be able to put on an amazing performance, have a great show, so that people want to walk out with your album and re-live the night over and over and buy your t-shirt so as to say "I was there". It sometimes seems music is being pre-fabricated, and if music is pre-fabricated, "fixed in the mix", then how can it not come from the brain instead of the heart? If your music, your performance, your reason for being in this business doesn't come from the heart, if you're trying too hard, you're not going to connect with your audience, you're not going to move the masses, you're not going to be heard above the noise!
I could ramble on forever but I will leave it at this. If you are interested in this post then I highly recommend watching a great documentary called "Before The Music Dies", I saw a screening of it a few years back and have been recommending it ever since.