The Rossignol for two guitars, played over two IP addresses
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Guitar 1 is played at one IP address and delivered to IP address 2,
which induces delay. Guitar 2 hears Guitar 1 at IP address 2 and produces
the second voice, which is sent back to IP address 1.
Guitar 2 is recorded at IP address 1 together with the original Guitar 1
at IP address 1.

The delay between Guitar 1 and 2 is in the range of 0,3 - 0,4 seconds, 
which of course is all to much and the duet is not in synchrony.

CONCLUSION
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You cannot play music together over the internet!

(You might play theatre, as delay of speech is not so critical.)