The Linux sound system, like most of Linux, has evolved from a simple system to a much more complex one. This chapter gives a high-level overview of the components of the Linux sound system and which bits are best used for which use cases.
Here are some resources :
A Guide Through The Linux Sound API Jungle by Lennart Poettering ( http://0pointer.de/blog/projects/guide-to-sound-apis.html ).
“How it works: Linux audio explained” by TuxRadar ( http://tuxradar.com/content/how-it-works-linux-audio-explained ).
Insane Coder posted an article in favor of OSSv4 State of sound ...