In a tiny single-engine aircraft like a Cessna, all the way up to a modern jetliner like a 747, it seems the cockpits of modern aircraft have at least 4 separate airband radios, for monitoring up to 4 different frequencies at once.
However, the cockpit has only one up to (rarely) three occupants wearing headsets.
When Ground calls you and says, "monitor Tower, on 121.65", Tower wants to tell you something from that frequency, but Ground also wants you to stay on their frequency.
By which mechanism are multiple frequencies monitored by one or more (fewer than the number of radios/frequencies) crew members?
all the running cockpit radios are heard at the same time, mixed into the same audio
- how to know which transmissions came from which freqs?
switches that cause exactly one of the radios to be "active" in the headsets at once, and the other ones are not heard in the headsets
- how to monitor multiple freqs this way, without missing transmissions or switching back and forth so quickly it would be unreadable?
I've looked around, but I can't understand how multiple frequencies are easily monitored at once, without running into the problems I mentioned in my guesses.
So how can a pilot alone, or a pilot with a first officer, listen for their callsign on multiple frequencies at once?