It looks like you are not using piCore but a derivate, piCorePlayer. In native piCore the built-in sound device not started by default to avoid such issues with an optional sound card, kernel module must be modprobed explicitely.
Also, in piCorePlayer you can manage sound devices via the WEB interface which is expected to work. If not, better to use the piCorePlayer site to get support for the player. You can also PM sbp, author of piCorePlayer.