I am looking for guidance for a sound system type question. The school I work at has two major concerts; each concert has a wide variety of sound needs, from vocal support for the choir to micing instruments for the ensembles, and a rock band setup. At the moment these are handled by a few different systems with all of the rock instruments sending out to their own amps. The major draw back to this is that there is no way to adjust the balance during the performance of the different groups. I have been asked to find a way to simplify the whole process. They would also like to find a way to have monitors setup that have a controllable mix to the individual. I am not even sure what kind of information to give to be helpful at this point most of my training has been in lighting I have been picking up sound as I go. I currently have a 24-channel board that is fed through a patch system. However, there are only 10 lines available on the stage. The Rock and Instrumental Music teacher would each like there own system that would then be pony into the main system. When they talk about this they also keep mentioning a back line, I am not sure if that is something extra they want or if it is the same thing. I was wondering if anyone could give me some advice or recommend some materials that I could use to teach myself more about my needs. Thank you for any help you can offer.