Mix Space
The idea is to try for the least crowding you can. If more than one component is present during the same beat of the music, then exact timing of each is pretty essential in keeping the whole mix out of the mud and keeping it sharp. We all know and love tight music, so there usually is more than one component on the same beat.
One key here is that a band playing live and creating a recording are two totally different things. Mix space must be given respect on a recording. Often times, less is more as far as the number of instruments present at any given time.
Inside this scope of thinking it's helpful to be conscious of the number of instruments you have in any one mix. For the minimum, generally speaking, you need the backbone instruments (drums, bass guitar and a rhythm instrument such as a guitar or keyboard), a highlight instrument (which could be a keyboard part, a guitar part, a trumpet, etc.) and a feature instrument (one that does not necessarily appear at all times within the song). Any more components than these will tend to make the mix too busy.
Sure, of course there are great songs out there with more than these, but this is just a basic rule of thumb. Also, many of you will be just recording straight-ahead rock with all instruments blazing. That's ok, the same rule of thumb can apply. See the article titled,
Tips for Audio Mixing: Find the Groove for mixing ideas.
