if you can't hear any particular colour of the song because some instrument is buried down too deep into the mix I consider it was composer intended.
yes maybe the case most of the time, but not always I think
sometimes, the mix does no justice to what the composer had in head
sometimes, it's even not at all what he wanted. the most famous example is let it be, remixed by Spector and Lennon against Macca's ideas
and sometimes the technology at the time of the recording wasn't enough "elaborated" to have all details audible. I am thinking about "old" recordings during 30's 40's 50's and even late 60's like on Hendrix or Beatles recordings for example
and when they can release some remixed stuff, they often say "that's how I wanted it sound, but at the time it wasn't possible"
Of course those low volume instruments were intended to be this way. It is important to understand what this phase-cancellation technique does: It cancels all signals that have the same volume on both of the two stereo channels. These are the signals that normally seem to come from the center, apparently coming from a virtual place in the middle between your two speakers, typically vocals, bass, bass drum,...
What remains are the signals that are mixed more to (= have higher volume on) one of the stereo channels, those that seem to come from rather the left or right side of the stereo mix. The more they are mixed to one channel only, the higher their volume will be.
To illustrate, here is an example: let's say we have three instruments - like guitar, vocals, and piano.
The guitar has volume 6 on the left channel, and volume 0 on the right channel - you will hear it only from the left speaker.
The vocals have volume 7 on both channels - so you will hear vocals on both speakers.
The piano has volume 2 on the left and 6 on the right channel - it is louder on the right speaker, it seems to come from a virtual position somewhere between the center and the right channel.
Now, you invert the phase of one channel and mix both channels together to a mono signal.
There will absolutely no vocals (as volume 7 from the left channel cancels with volume 7 from the right, like 7 - 7 = 0)
The guitar will have volume 6 (6 - 0 = 6)
The piano will have volume 4 (6 - 2 = 4)
The resulting mix has compeletely different volume relations between all the instruments (guitar 6, vocals 0, piano 4).
If you want to hear music this way you can solder a little headphones adaptor cable, with a plug on one end and a jack on the other. The jack / plug has three connectors, left, right, and ground. Leave the ground on the plug empty, connect right on the plug with both left and right on the jack, and left on the plug with ground on the jack.
Then just plug your headphones into the jack on the adaptor, and the plug of the adaptor into your stereo device, and voila.
