Alice,
I believe you are supposed to include a first and last name, as I would bet dollars to navy beans that you are not the only person in here by that name.
I am a musician as well, and I can tell you that back in those days, many more people learned to play an instrument. These days there seems to be so many that are self-taught, play music via a "fake book" and ad-libbing with whatever the chord progression is, and there are even famous musicians that can't even read (or at least sight-read) music. Music instruction in schools is leaving us as fast as WW2 vets are, and the thing that really gets me annoyed is how someone will take a perfectly good song that has been successful, sample it and loop it, and then babble along with it spewing nonsense, and calling it ART. oops, I really went off on a tangent!
Okay, what I was really getting at is back in those days there were no I-pods. The popularity of a song was gauged by how many copies of the sheet music that was sold, and to a lesser extent, piano rolls. Practically every house had a piano in it, and someone in the house could play it. Sadly, this is going away. I would say the short answer would be; a good guess is that probably 10 or 15% of all the people on board,perhaps more, could play an instrument. Not all virtuosos, but more than you would find today.
I had the distinction of winning the Titanic trivia contest, and the silly talent show on the last cruise I was on!