No startup / boot chime; how to bring it back?

Consider trying this out:

1. Launch Terminal.app and type the following command:

   sudo nvram StartupMute=%00

2. If prompted enter the admin password.

3. Quit the Terminal app..

4. Make sure the volume is up before you restart your Mac.

5. Restart your Mac.

You should hear a F-sharp chord sound when your Mac boots up.

If you wish to disable it, follow the same steps as above and type the following command instead:

sudo nvram StartupMute=%01

_{Tested on a 16" 2019 MacBook Pro running macOS Catalina 10.15.3}

Unfortunately there is no way to bring the startup chime back (although I'm happy to be corrected).

As for the BootAudio command, it never actually worked! ^{1, 2}

However, the AutoBoot option is still available. In case you don't know, the AutoBoot command can enable/disable the MBP from booting when the lid is opened. You can use the AutoBoot command as follows:

• Disable auto boot: sudo nvram AutoBoot=%00
• Enable auto boot: sudo nvram AutoBoot=%01

Personally I would leave Auto Boot on, but that's a personal preference.

¹ - I've never seen it work on a single 2016 MBP since they first became available, and I've had my hands on many!

² - See 2016 MacBook Pro: Enabling the Startup Chime... does not work. Note this was published on 18 November 2016, and remember the 2016 MBPs were launched at an Apple Event on 27 October 2016. So we have users confirming the BootAudio command isn't working within 3 weeks of the official launch. Keep in mind the MBPs did not ship for a while after the event as well. So, when did it ever work?