This specification is currently being experimented.
XEP-0085: Chat State Notifications provides a way for notifying a contact when you're composing a message. It might be nice to let your buddy know whether you are composing a text message or an audio message.
In Kontalk, you add the standard composing node plus a custom audio recording node.
<message type='chat' from='[email protected]/home' to='[email protected]'>
<composing xmlns='http://jabber.org/protocol/chatstates'/>
<recording xmlns='http://kontalk.org/extensions/message#chatstates'/>
</message>