Lesson 29

Summing Audio

Summing is an often overlooked part of the recording process, or more specifically.. the mixing process. 
When a song is recorded, it will have individual tracks for each part. Those tracks are all played back simultaneously and heard as a single stereo track. At some point, all those tracks need to be merged together. This part is the summing. There are 2 main methods of summing. Analog, and digital. Analog summing uses a traditional analog mixer. If the song was recorded into a daw, then during mixdown, each individual track is routed to its own dedicated output, which goes to a channel in the mixer. The song can then be mixed on the mixer, and the stereo output from the mixing board is recorded back into the daw. Analog summing is commonly referred to as “Out of the box”. 
Digital summing is simply using the computer to merge all the tracks together. This is done seamlessly within any recording program, and is often not even a consideration. Digital summing is often called “in the box” It’s important to know what’s going on though to know the advantages and disadvantages and of both types of summing.

Digital summing, aka “in the box”
Uses a mathematical algorithm to sum all the tracks together. These algorithms have limitations, set by the bit depth in which they take place. Higher but depths will provide values with more decimal points, and therefore more precise, and less rounding off. However, no matter how high the bit depth, it will never be capable of infinite values, and will always round off to some extent.

Analog summing “out of the box” 
All the tracks are played through individual outputs, routed to the mixer, or summing box. These outputs will go through some simple electrical circuit that ends up routing all the tracks together, and they are naturally summed together. While this method is theoretically more precise, because analog offers infinite values, but there is noise created from the electrical circuits. This noise is detrimental to the sound quality, and is the main drawback of analog summing.

Many people find there is no difference between the 2 types of summing, and are therefore happy to simply let the computer take care of it for the convenience, or Inversely, they don’t want to deal with the inconvenience and expense of setting up analog summing. On the other hand, some engineers prefer the feel of mixing on an analog board, and some will say they prefer the sound. There are professional mixing engineers who make a living using both methods.