Have you tried simply learning the bass lines to a song you
like and learn to play it all the way through?
By all means take the high road and learn music theory
and how to sight read music notation but I can't stress
simply trying to cover tunes as part of the learning process.
By doing this you will get an understanding of how songs
are put together as a complete structures such as what
chord progressions are in the song and how the bass player
moved that chord progression as well as being part of the
rythmn section etc.
You can buy song books for a lot of artists or you can also
do what most of us have done and that is to put on a recording of a song and start copying the bass parts by ear.
Learning how songs work as music is what it's about for us
bass players or any musician and it will take you beyond
the really cool slap solo stuff and other little licks and bits
you've learned but haven't been able to translate into being
part of a band as a player.
