We have all of our mics and tracks set up and are ready for a recording session. The artist wishes to use several instruments that occupy the lower registry of the bass clef and low end of the frequency band. The artist wants to record cello, bass guitar and large drums for his session. While this is possible and completely doable, it isn’t recommended. The reason why this isn’t recommended is because all of these instruments are low frequency and low voicing instruments. They all perform bass parts and will immediately step on each of the other frequency ranges that the other instruments need. This will cumulatively lower the amount of dynamic range allowed for each instrument.
In this case the artist wants to use several bass instruments and all of them sound like each other with few exceptions for tone color. A great recording uses the full spectrum of tone color and frequency ranges but doesn’t load up any one band with too much information. Your tracks will be summed at the master output so all of that bass from all of those instruments will create a cloudy, muddy mix if not properly shelved in the EQ stage. The best technique in this situation is to lower all tracks below the sum on the master tracks and attempt to blend each track with the sum of all tracks without clipping the master channel. If you can pull this off with transparency between the instruments then you are well on your way to being a professional audio engineer. The point is that so much range that is needed for individual instruments will be divided across the sum of all instruments leaving individual tracks without impact and dynamic range.
The trade off is less dynamics and volume and depending on how many of these tracks you have that will be mixed. If there are too many instruments it won’t matter what you do because the sound will be convoluted and messy. Orchestrations of classical music use a lot of different instruments, tone color and frequency range and if you listen closely you can tell that a recording of an orchestra is lower in volume than a five piece rock band. It isn’t because of the genre, it is because of the number of tracks that need to be summed at the master channel. The more instruments used and the type of instruments used will determine how much volume each individual instrument will be able to use. Every time you add an instrument it takes up some of the frequency and volume range available for all of the instruments.
The best rule of thumb is keep it simple. Use instruments that compliment each other like a cello and a flute. The cello will use the lower frequencies and the flute will use the higher frequencies. You may lose some of the available volume ceiling but the use of all frequencies in small slices divided into voicing sections between all of the instruments will produce the best results. The same applies for a rock band. Use only what you need and spread the use of frequency across several instruments and the vocals. Take some of the bass out of the guitar track and some of the treble out of the bass. Work each track the same way reserving enough volume ceiling for all of the tracks during the mix down stage.