Making up bass lines on the spot is a skill that you can learn without too much difficulty. You need to know the right things though and that's what this bass tutorial is all about.
This bass lesson is quite similar to a popular video I have on YouTube about how to create bass lines.
Here's that one:
Creating Basslines Over A Chord Progression (Bm/G/Em/C)
You're about to learn how to make bass lines up going from simple root notes to more sophisticated rhythms and scales/arpeggios.
It's a lot of fun as well as a highly useful skill.
Scroll down for the free backing track and PDF.