I now know why Mom enjoyed signing along to the muzak at the store. Because it annoyed me.
A few days ago I went to IHOP with the folks and baby Sis. Sis was complaining about the music we, the adults, like. Started out complaining about "40s music", i.e. Big Band jazz, and then said something about that "O-de O-de Oh" song. At first I was completely confused and then it hit me the goatherd song from The Sound of Music. So, of course, I said "do you mean?" and started singing. She started saying "no", "stop", and other cries of general anguish. As I opened the door she asked that I please not sing in the parking lot or restaurant. So I sang right up until my head went out the door, then leaned back in picking right back up. I repeated this action several times to her horror.
It was GREAT.
Now I understand that when it seemed like my parents were doing something just to annoy me, they were. One of the secret pleasures of parenthood.