In mixing (but this is not a must, I must warn you), you normally start with the foundation of the song. And that normally would bass and kick. The reason why input ! and 2 are those. Then snare. then toms, oh, etc. Although this is not really how things are to be done, to make things easy, this kind of arrangement is followed. Also, the edge of a tape, say 24 track tape, normally, would, a lot of times, be bent or damaged, which results to loss of high frequency. And since bass does not need any HFs, that is where it is most logical to put the bass track. This was how it was during the analog days. Now that these things do not happen anymore in the age of digital, any input position can be used and it does not matter. It is just what you are used to in recording or mixing. To date, I still follow the old assignment technique as I find it most logical and follows a step by step procedure. In mixing, I always start putting up the vocals, wherever input they are assigned, process and eq, etc. them, and when finished or I am satisfied with how they sound, follow the step by step technique of putting up the faders of the bass, kick, etc. To each his own. There are no rules in mixing. FWIW
