Try this:
Here
https://docs.lmms.io/user-manual/gettin ... o-settings
Set your devise to SDL
If your issue continues please let us know your version of lmms
Besides that, since you are new in Forum
Welcome qed3 !
Here are all important links:
http://lmms.io/forum/viewtopic.php?f=1&t=4740
-A few rules and useful forum instructions
If you like to introduce yourself, to the community, go here:
http://lmms.io/forum/viewtopic.php?f=4&t=4480