Quietly is a simple addon that defines the /q console command, intended to be used in macros to temporarily suppress error messages and "I can't cast that yet" error sounds.

Using the /q command instead of the longhand saves over 90 characters, giving you much more room to work within WoW's 255-character limit for macros.

As an example, here's a Wrath Classic macro for a troll shadow priest to pop all available off-GCD cooldowns and start channeling a big mind flay in a single keybind:

>#showtooltip Mind Flay
>/q
>/use Berserking
>/use Inner Focus
>/use 10
>/use 13
>/q
>/use Mind Flay

Even if one of the cooldowns isn't up, there won't be red error text or an "I can't cast that yet" voiceover. Hooray!

The first /q is equivalent to:

>/console Sound_EnableErrorSpeech 0
>/run UIErrorsFrame:Clear()

And the second is equivalent to:

>/console Sound_EnableErrorSpeech 1
>/run UIErrorsFrame:Clear()

Note that you don't actually have to include the second /q in your macro. It will happen automatically after your macro completes. You only need to explicitly include the second /q if you want errors enabled for the final part of your macro.