To go further, with your question about alsa--
It really depends on your soundcard. Some soundcards have multiple channels for input, whereas some soundcards have only one.
Mine happens to have 4, which surprises me because it's a cheap onboard AC'97 knock-off. Alsa is perfectly capable of using all the input channels. Mine are controled by using alsamixer, and moving all the way to the right, where I see several DXA channels, 1-4.
If your card has only one, then the only solution I know of to have two programs access sound at the same time is with what's called a sound server. It combines two sources and mixes them down to one, which gets sent to the soundcard's single channel. Esound (gnome/enlightenment), Arts (kde), and JACK (pro audio applications) all do that.