Newbie palette question

Hi
What is that second layer of palette options that appears on the bottom - i.e. tabs like guitar, percussion, brass etc? They appear in the video tutorial, but not on my copy. I assume they are something to do with third party libraries, but I'm not sure.
Thanks.
What is that second layer of palette options that appears on the bottom - i.e. tabs like guitar, percussion, brass etc? They appear in the video tutorial, but not on my copy. I assume they are something to do with third party libraries, but I'm not sure.
Thanks.