That top letter is exactly the sort of thing I'd send...
Thank you for agreeing to play at our charity bake sale. If you don't mind adding a bit of Xenakis to your regular setlist, we'd appreciate it. 'Concret PH' would go down a treat after 'Mustang Sally' and a bit of 'Akea' would be great if you've got fifteen minutes to fill, a pianist and spare string quartet handy.
My wife discovered she likes Zappa yesterday. I played The Grand Wazoo for her because of the wedding requests letter. She then proceeded to play more Zappa for about 2 hours while I worked on the kitchen.