I think that playing music of the past can be completely ethical, as long as you don’t try to pass off the music as your own. If you were to perform one of these works that have disappeared, I believe it is only ethical if you give credit to the original artist, almost like they’re your “ghost writer”. You wouldn’t play something by Bach, for instance, and claim that you composed the music yourself. You should credit the original writer, possibly as a lesser known composer so the name doest come out of nowhere, to remain ethical. If you act like you created all of the music yourself and even became famous, people could somehow find out you actually didn’t, you would be seen as a fraud and a liar. This could end up tarnishing the reputation of the music itself and it could even lose all of its artistic value as a whole.
With easy multi-tracking technology of today, you can easily create and release music with multiple parts, and not have to worry about only performing things for only solo instrument or a polyphonic instrument with voice. It’s difficult to list all of the music that I think should be performed, but here are a few:
Toccata and Fugue in D Minor – J.S. Bach
The Girl From Ipanema – Stan Getz
Here Comes the Sun – The Beatles
This is only a small amount of music from the past that I believe would be very important to play in the modern day. I think that these cover a few different cultures, as well as a fairly wide time period. The list of music would go on and on for much longer if I included pieces from more cultures. None of this music is necessarily more important than others, its just the first few I came up with while thinking of historically important music.