Try with headphones, and check the mixer… IIRC with opensound there may be many options there, could be some need un-muting. But also perhaps @PulkoMandy can advise as he has a similar (the same?) laptop I believe. I have an x240 here, where I’m fairly sure sound worked fine last time I tried.
You’re looking at the first code-box in the docs which gives its syntax, where “…” stands for optional additional entries. The next code-box and the following example show the actual usage in an example.
In your case the text file /system/settings/packages that should read:
I just tried this in my X220. If the audio is stuttering, in the process controller widget -> Threads and CPU usage -> MediaPlayer -> MediaPlayer or MediaPlayer audio ou controll and set it to real-time priority.