Sorry if offtopic...
Whether there is internet service for making music together? Looks like transfer midi online to and from internet with low latency?

hmm... don't know what you want, but you could use skype or something like that.

That is a good idea. It can work over a local area network with in a building or small campus. there is even a common standard for MIDI over a network.

But you'd never be able to get good enough latency over the Internet. You can test the best case latency with "ping". In theory MIDI could travel no faster than the ping time to the other location. It's not the data rate it is the latency in the network that is th problem

If you wanted to do this you'd be much better off using a direct link to the other, remote location over "POTS". "Plain Old Telephone" (not skype or VOIP) but even then the speed of light delay it you have to up to a satellite.

I think for most of use emialing a MIDI or MP3 is the only option.

Many people play online games (and my daughter..) and it's latency (in my connection) about 20-40ms (some times more). And I think about use internet not for gaming only but playing music also. I think this idea not originally
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Try searching "USB over internet".

I suppose you can connect your DP to a local PC using USB and the PC connect to another PC using proprietary software as USB bridge and then you can playback the sound over the remote PC through MIDI.

But I really doubt it would work well given all the network jitters. You may not notice the jitter over online games because they are optimized to handle network problems.