Hi Samit,
big apology for not answering your question before now - for some bizarre reason I just didn't see it...
passing tones in walking bass... first up I'll say that lines just using the 1,3,5,7 arpeggios can be great, and it's probably a good idea to get really comfortable with those before moving on...
after that, you can start to add the extensions to each chord - we've already got the 1,3,5,7 and from the key that we're in, we can add the 9,11 and 13... EG - in the key of C, a CMaj7 chord is C,E,G,B. if we keep adding alternate notes above that in the key that we're in, then we get D,F and A aswell before we come back to C; D is the 9th, F the 11th and B the 13th. What does that give us? it gives us a 'harmonic' reason for using all the notes in the key of C against a CMaj7 chord. You can oversimplify this by saying 'just use the notes in the key that you're in', but then you get stuck if you suddenly see CMaj7#11 and thought you were in the key of C - what do you do with that? well, if you're thinking of the F as the 11, you just sharpen it - no need to switch brain into 'oh, er, #11 chord means Lydian mode'... just play an F# instead of an F...
This also means that you can make your own alterations that aren't written... Still in C, if we 'stack thirds' on top of D, the first four will give us a Dmin7 chord - D F A C and the next three are the extensions - E G B; E is the 9, G the 1 and B the 13... if we're moving from Dmin7 to G7 (as in ii-V progression in CMaj) - we might want to alter some of those notes in the Dmin chord to 'lean' into the G7 chord. again there are two ways of looking at this - firstly, we can take the simplistic way, which is to say that any note in the Dmin chord that is a tone away from the target note in the G7 chord can be sharpened or flattened to lead in my a semitone instead of a tone - EG, if you're walking on the Dmin, make the last note of the chord an Ab to lead strongly onto the G - you can play D, C, A, Ab through the bar, or D, E, F, Ab or any other combination. you could do the same with sharpening the third and walk up D E F F# or D A F F# etc...
However, each time you change a note like that, you change the chord, and if you learn what those altered chords are, and what they sound like, it makes transcribing, improvising, folowing the subsitutions played by other musicians and sitting in with other bands much much easier. If all you're thinking is about semitone lead in notes into the next chord, your line may sound fine, but your connection with the music will be less. So you can always learn it the easy way and the 'reverse engineer' the theory side of to work out the harmonic effect of the notes that you're using to lead in...
I hope that makes some sense - it's by no means thorough or complete, so feel free to come back with further questions, or even better, get 'The Improvisors Bass Method' by Chuck Sher.. :o)
cheers
Steve
www.steve-lawson.co.uk
