You might try in Yast, Sound. There are sound cards defined.
Check if they are setup. Pulse Audio might be a good idea.
Maybe you can test if there is sound in general. You can do that via Yast. Test sound.
Be sure the is a hole through. :-)

You can in fact use Rythmbox. This piece of software can more than you believe. As usual, not good documented. But there are and can be established radio stations you can listen. They work.
This might be a good tool for test too.

But this is not enough. All music on Web and otherwise comes packed in codecs. These Codecs are not part of SUSE.
I think I wrote somewhere here how I installed my system (against all SUSE rules).
My experiences is best to install:
Adobe Flash for be able to see video.
Install VLC player, but NOT from SUSE or OpenSuse. Only from original VLC-Player in version Leap 42.1 or Leap 42.2 or from packman repository that have some repository for SLED12 too. (I used the original videolan.org)
Further I installed ffmpeg too - think it was from packman too.
VLC brings most of needed codecs and is a standard in PC world, both Linux, Android and Windows. This works. (Eventually you need in Yast Software Management search for VLC or codec install codes extra)

To make installation not to a pain, I pre-installed Leap42.2 OSS, NON-OSS repositories. Otherwise you end up in many missing dependencies - a really mess!
VLC will install some new repositories.
All these I placed in priority 100 in Yast respository , so the system takes SUSE software repository before Leap and videolan (priority higher means lower in choice)
When all is installed I disable the foreign repositories again, but keep them when needed later. So they get not selected when running updates.

There is a risk for instability. But unfortunately Linux still is made more for developer and less for user. There is a lot of "standard software" missing. But we have 3 types of terminals in SLED!
I hope this will change over time so SUSE get's a competitive product. Basically it works well - after some effort. :-)
Be aware, SLES has a software Hub that works on SLED too. here, lot of proven software can be found too.