Ardour is by far the most professional free and open source audio production tool you will find. JACK is also going to be an integral part of any audio production environment you set up on Linux.
This tutorial will teach you the basics of how to use Ardour and JACK together to record/produce music. While you might consider this a "tool based" tutorial, I would suggest giving it a chance. Producing music on a computer is essentially combining the right tools; and this tutorial teaches you how to use the two most powerful open source tools with very simple, practical and easy to follow directions.
The Linux Musicians forum is also a great resource for learning how to create music using open source tools. I would highly suggest creating an account there and looking around.
This site has some nice basic audio production tutorials. They of course aren't using Linux, but you'll notice that versions of all the plugins they talk about are available in Ardour.
Welcome to the wonderful world of open source audio production and good luck!