OK. I was speaking from my own experience from a couple of years ago, and I don't recall that appsrc/appsink existed at that time.
Still, I don't think that it is obvious how one should port an audio app using another audio API (ALSA for example) to use GStreamer for output. GStreamer seems to be designed more like a toolkit which you have to design your app around (like GTK for graphics) rather than just the audio bottom layer that most other API:s provide.