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Here you can find information regarding CTAG audio cards (FACE and BEAST) in combination with ALSA drivers (native Linux audio backend).
A ready-to-use Debian based SD card image can be found here. The image includes evaluation tools, JACK, SuperCollider and other useful tools.
Instructions how to flash the image to a SD card can be found in the BeagleBoard Wiki.
If the BeagleBone is connected to a machine via USB, the machine should get an IP address via the DHCP server running on the BeagleBone. The IP address of the BeagleBone is 192.168.7.2. A connection to the BeagleBone can be established using ssh. The username is debian and the password temppwd.
The audio card drivers (i.e. kernel modules) have to be loaded via a device tree overlay, which configures the audio card drivers. There are two different device tree overlays for the FACE version (8 channels) and BEAST version (16 channels). The file names of the dt overlays are BB-CTAG-SW-8CH-00A0.dtbo and BB-CTAG-SW-16CH-00A0.dtbo for the FACE and BEAST respectively.
A device tree overlay can be loaded via bone cape manager (included in all SD card images by BeagleBoard):
sudo echo BB-CTAG-SW-8CH > /sys/devices/platform/bone_capemgr/slots
By default, the BEAST overlay (BB-CTAG-SW-16CH) is loaded during boot.
This can be changed in /etc/rc.local (e.g. comment line if you want to load the drivers manually).
The other lines (e.g. echo 0 > /sys/class/gpio/gpio81/value) are required to reset the audio codec(s) via GPIOs at each boot. Thus, they should always be present in /etc/rc.local.
After the device tree or rather the drivers have been loaded, the audio card can be displayed via aplay -l. Now the audio card can be used like any other audio card under GNU/Linux.
The audio channels of the audio card can be accessed via ALSA hardware interface (i.e. hw:0). Every application (with ALSA support) can use the audio card now. In the SD card image, there is only a single audio card available. Hence, every audio application should automatically select a CTAG audio card as audio backend.
ALSA provides several test tools for audio cards. To test the audio card speaker-test can be used. speaker-test generates a test signal (e.g. sine with specific frequency) and outputs the test signal on a single channel for a specific duration.
Furthermore the SD card image includes a multi-channel delay example project based on DSPatch. The multi-channel delay can be started with /home/debian/multichannel-delay.sh. This is also a good starting point for developing own ALSA applications.