Send sound output to application and speaker

I'm using my Ubuntu 14.04 LTS Laptop toplay music at a party. I'm using Mixxx and is performs very well for that task. Now I'd like to add some light effects and plan to use Qlcplus for that. So I need to send the sound from Mixxx to the soundcard and Qlcplus.

I've managed to configure Mixxx to send sound to the ALSA loopback and recover it from there in Qlcplus. But then I have no sound output. How can I route sound from the ALSA loopback to speakers ?