How do you turn off a speaking keyboard

In the System Preferences> Universal> you should be able to
control the voice actions; and turn them off or on. Some of
the keyboard commands to activate these items can be found
by accidental touching certain key combinations.

Oh, I had to read your post twice, to see you are describing
the use of an older iMac G4; since I saw the OS X in your
signature line as one not capable of running in these...!

What OS X version is running in the G4 iMac?
The path to turn off voice should be the same
in Panther, Tiger, or Leopard 10.5.

Good luck & happy computing! 🙂

+{ edited }+

However, on looking through some items in Tiger 10.4.11, there
may be a setting in another location; I've never had keys speak.
But do know such settings exist, to aid those with disabilities.

{The keyboard shortcut command+F5 is what toggles it on/off.}

In OS 9.2.2 & before, it was easier to mess around on purpose
and make almost anything speak; and have the OS read it aloud.

If certain keyboard combos were accidentally pressed, it's possible
to have turned on Universal Access> Voice over commands. If you
were unable to make the talking go away from that System Prefs
panel, post back and specify what was tried.

Here's an example of one or more instances of accidental VoiceOver
by keyboard combo happenstance, and one of them involved another
key change. Not knowing what else may be going on, you can check
into the topic by simple online search...

• How to turn voice off for menus?
http://forums.macrumors.com/showthread.php?t=450898

Perhaps another can refresh the collective consciousness in the
matter of where else to look to disengage and engage the audio
interface which makes keys speak as you keyboard in OS X.

Hopefully this helped somewhat.
Good luck & happy computing! 🙂