Messages becomes much more exciting when you exploit its AV Club capabilities. Even over slow Internet connections, you can conduct audio chats, speaking into your microphone and listening to the responses from your speaker.
If you have a broadband connection, though, you get a much more satisfying experience: Up to 10 of you can join in one massive, free conference call from across the Internet.
A telephone icon next to a name in your buddy list tells you that the buddy has a microphone and is ready for a free Internet “phone call.” If you see what appear to be stacked phone icons, then your pal’s Mac has enough horsepower to handle a multiple-person conference call.
To begin an audio chat, you have three choices:
Click the telephone icon next to the buddy’s name.
Highlight someone in the buddy list, and then click the telephone icon at the bottom of the list.
If you’re already in a text chat, choose Buddies→Invite to Audio Chat.
Once your invitation is accepted, you can begin speaking to each other. The bars of the sound-level meter let you know that the microphone—which you’ve specified in the Messages→Preferences→Audio/Video tab—is working.
Although the audio is full duplex (you can hear and speak simultaneously, like a phone but unlike a walkie-talkie), there may be a delay, like you’re calling overseas on a bad connection. If you can’t hear anything at all, then check out Messages’ Help system, which contains some suggestions.