Trying to use Automator

[Doc]

No brackets and it's case-sensive so the Users and Music folders start with a cap.

...And there's a space after afplay.

Also, since you've put a space in the file-name, you'll have to escape it with backslashes or change the name to remove the space.

It should look something like this (assuming that the name of the file is correct):

do shell script 
afplay /Users/emdc/Music/Mac\\ startup.aif