No, that is not how to works. You have to setup channels with whatever frequencies you wish to be available. So, if you are the server owner/admin, you would setup channels for the frequencies you wish to use. For example, if I wish to have radio frequencies available for ground, tower, and CTAF I would setup channels as such:
Once setup when someone joined the server and tuned their radio to one of these frequencies the comms program would place them in the channel associated with the frequency. This assume the person joining the server was running the comms program.
The comms program doesn't not provide the capability to monitor/hear two channels/frequencies at the same time.
I hope that helps.