If you do not perform, redistribute, sell, or publish any of the songs you have 'played' with, then nobody would object. But if you have or mean to do, and you only have changed minor details, then you can not do that without written consent from the original composer.
Besides that, since you are new in Forum
Welcome Onething !
Here are all important links:
http://lmms.io/forum/viewtopic.php?f=1&t=4740
-A few rules and useful forum instructions