Meaning of the Activity and Power LED's on a Pi while Volumio is running

This is hopefully a quick question as everything is working OK, but I am curious as to what the blinking LED’s on a Pi (3A +) mean while Volumio is running. Generally speaking the red Power LED and green Activity LED’s are off but every so often they come on for a couple of seconds (or blink for a short time) before going back off.

I see from the plans page that the Volumio system is “loaded entirely on RAM” so the Activity LED blinking from time to time surprises me a little once it’s up and running.

At the moment I am only using it as an Internet radio and using the headphone socket on the 3A+ to provide a source to a powered speaker. I wondered if the LED’s are performing some kind of indication as to the buffer state for example, but cannot see a pattern to their use nor can I find it documented anywhere.

Has anyone else been able to determine the function of the LED’s ?