I've been playing bass for about a year now and most of the songs I play, I'm just banging away on root notes. What are some ways I can expand my bass playing?
learn more complicated songs, increase your vocab of music by listening/playing everything from metal to jazz. You will eventually find some very exciting/ complicated bass lines that you can have fun learning.
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Everton FC
If you haven't already, start working your scales and modes. From there, work your scales in broken thirds, fourths, fifths and sixths. Work on your arpeggios and chord understanding. This should give your understanding of how to start building a basic walking bass line, which is the foundation for starting to develop your own basslnes.

For more info check out Jazz_Rock's thread on walking basslines:

Practice definitely won't help...anyone who says otherwise is a liar.

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