Here's a way to use AppleScript and the 'say' command to have the computer sing happy birthday to you. Enjoy!
set currentUser to long user name of (get system info)
set firstName to first word of currentUser
set lastName to last word of currentUser
set noteValues to {56, 56, 58, 56, 61, 60, 50, 56, 56, 58, 56, 63, 61, 50, 56, 56, 68, 65, 61, 60, 58, 50, 66, 66, 65, 61, 63, 61} -- F
-- set noteValues to {65, 65, 67, 65, 70, 69, 60, 65, 65, 67, 65, 72, 70, 60, 65, 65, 77, 74, 70, 69, 67, 60, 75, 75, 74, 70, 72, 70} -- D
-- set noteValues to {55, 55, 57, 55, 60, 59, 50, 55, 55, 57, 55, 62, 60, 50, 55, 55, 67, 64, 60, 59, 57, 50, 65, 65, 64, 60, 62, 60} -- E
set syllables to {"hap", "p", "birth", "day", "to", "you", "[[slnc 500]]", "hap", "p", "birth", "day", "to", "you", "[[slnc 500]]", "hap", "p", "birth", "day", "dear", firstName, lastName, "[[slnc 500]]", "hap", "p", "birth", "day", "to", "you"}
repeat with i from 1 to the length of noteValues
set thisValue to item i of noteValues
set thisSyllable to item i of syllables
if length of thisSyllable is less than 3 then
set speakingRate to 220
else
set speakingRate to 100
end if
say thisSyllable pitch thisValue using "Cellos" speaking rate speakingRate modulation 0
end repeat
Mac OS X Hints
http://hints.macworld.com/article.php?story=20120204172337402