On Facebook, you can opt to have your birthday show up as a notification on your Facebook friends’ Home Page on the day it is your birthday. Most people then just usually write something short, and frankly, a little meaningless from how generic it often is.
The person whose birthday it is, then, gets like a ton of notifications of these greetings. They may or may not go through them all, as most are the same old plain “Happy birthday!” variation. But what do you expect of mostly shallow “friendships” that come with most of most people’s Facebook “friends”?
However, some people go through all the comments so they don’t miss something they may want to respond to, or should acknowledge to avoid embarrassment of not having read it when someone took the time to write it… and asks about it later.
What I’m proposing is that if you want to be a little more genuine, and break the person’s routine scroll through all the relatively meaningless wishes a bit, add a little song link, like from YouTube. A lot of songs can be found there.