Very interesting discussion.  I am just learning.  Books, articles, videos, hand-on etc.  Trying not to get caught up in vendor hype or personal bias, especially with plugins.  But while I was reading this thread, I was thinking a bit about the big picture as I understand it so far.  Something like this:

Good Musicians => Good Recording => Good Mixing => Good Mastering.

Without good musicians, everything down stream really doesn't matter as much.  I hope I don't lose sight of big picture, as I am deep into learning details some sophisticated plugin.  Forest from the trees, branches, twigs, ...

Staring with Good musicians and recording of same is the key, everything else can be fixed.

Sorry for stating the obvious, I am just in novice learning mode.

Peace Out.

Guitarpima


If you want to know what frequencies are occupied by an instrument then you need to download a frequency chart. Just do a search. They are very handy to have but again, use your ears.

I think an analyser like Spam does it much more accurately. Samples of a certain  instrument  from different manucacturers or respective patches in different synths may sound very different. IMO, a frequency chart is truthfull only when you use very "au naturel", dry samples of acoustic instruments. Even human voice with the same mic varies much depending on the amount of proximity.
 
Also, an analyser can be very necessary if your monitor speakers can't reproduce low enough, so you learn to spot rumbles that are inaudible in your system but may be very disturbing in other reproduction systems. Often such rumbles don't disturb you when checking with headphones, but enhanced by room acoustics they can sabotage the mix.
 
Having used an analyser for some time you learn the tricks and need it less and less.

I think an analyser like Spam does it much more accurately.

Cue the Monty Python songs!

I take it you mean Voxengo Span