Hello Hayden, can you explain please when practicing this bass line technique on beats 2 & 4 , is there a specific formula we adopt in choosing which (bass) notes to use, or use Root & 5th where possible, &, where there are 2 chords per bar, use Root on 1st chord ,with semitone approach note to 2nd chord in the bar?
Great question here @niall
Whilst there is no set-in-stone formula for building walking bass lines here are some general guidelines to follow:
Outlining the root & 5th on beats 1 & 3 is perhaps the simplest way to create a bass line - I like this because it leaves lots of space for the melody as in the example lesson you reference.
Approaching from a half step above is also very effective. For example try alternating root & 5th and then sometimes just approaching the root of the next chord from a half step above.
In a minor 251 progression, the b5 of the ii-7b5 chord is a half step above the root of the V7 chord, and the 3rd of the V7 chord is a half step below the root of the i-7 chord, and so this half step motion works particularly well over minor 251s.
In major 251s we can play roots and 5ths with chromatic passing tones to connect you to the root of the next chord.
Be mindful of the contours of the bass line, you can move up or down and alternating directions can create some interesting effects.
I’d recommend checking out this lesson taught by Robert on walking bass. He gives some really great insights into the role of strong notes, chromaticism, chord tones, and encolsures:
Robert is playing the hammond organ but all of the principles he talks above are equally applicable to the piano. His lesson on improvised lines resolving into chord tones is also worth watching
I hope that helps Niall - any further questions let me know