After reading a bunch of posts here about theory and what to play over different kinds of changes and how to make walking thru modal tunes or minor blues interesting I wanted to offer something... When I was younger and voraciously trying to get the theory of jazz into my ears and brain, i went to the Berklee school of music (studying vibes at the time with Gary Burton) and then bass with Charlie haden and Dave Holland and a bunch of other cats in NY... What happens after a long time of thinking about how to play over changes is that you discover that pretty much all the 12 notes are usable and available at any given time over any given chord ( I realize this is no help...) but what you begin to notice when you really start listening and transcribing a lot, is that your favorite players are using simple strategies to create melodies. The basic strategy is play chord tones. If you play only chord tones you will never play a wrong note etc... But check this out, if you are playing jazz on any instrument but particularly bass, probably the single greatest facilitator ( the most useful strategy) of playing right notes at the right time and creating interesting moving lines (while keeping the music pulsing) is the use of the bebop scales ( chromatic tones added between the diatonic notes in specific places so that harmonic rhythm is kept on the strong beats) if you learn the bebop scales for each chord type and play (only) them when you practice and play jazz, you will quickly find that a lot of the dead end streets that your fingers find themselves walking into are automatically realigned, that your ability to solo in complete sentences and melodic ideas is greatly increased and that suddenly you are speaking the same language as the melodic instruments in the band. After a whole lotta years looking at harmony and chords and listening and transcribing, I hear the bebop scales and the simple elegance of using the right passing tones as the fundament of improvisational fluency. If you learn the bebop scales for every chord type and practice your scales and tunes using them (That is to say if you are practicing a major scale then always add the flat 6 tone as a passing tone between 6 and 5 etc.) You will quickly begin to eliminate awkward passages and replace them with smooth even phrasing and chord placement. Bebop scales enable pulse to happen without shifting the chord tones to the weak part of the beat, and are for the walking bassist the most essential elements. And weather it is called by this name or some other it is the essential language of jazz that everyone uses Playing bebop scales and listening to them and examining their logic is surely a quick way of learning the essence of the way this language is expressed. Anybody have any thoughts on the matter?