How can I display a scoreboard on stage for a play?
Just get a programmable LED display much like this one, and an audio amplifier and speaker. Hook these up to a PC, and do it all in software. You can play samples through the PC's audio line out to the amplifier to make whatever sound you want, and talk to the display over RS-232 to make it display numbers.

Forget Arduino, custom electronics and so on. This does not have to be an embedded hardware project.