I don't know if this is widely know, but Reaper has some plugins that permit playing with other players over the internet. I routinely jam with folks from UK, Europe, Brazil, Canada and US. Even with folks from Australia (that led to collaborations too).
It works by BPM and BPI. So you play stuff to metronome or drum beat or other players you're hearing - you audio doesn't show up until one complete BPI an interval of a number of measures. It works well if the main theme is played and matches the BPI so others when they join and play, won't be heard until a complete interval. In this way there is absolutely no delay.
