I've been playing bass for a couple of years now, learning mostly from tabs. Now I've turned to actually trying to learn more than robotically copying bass lines without understanding them. I've started with scales but, having thought I was making progress, I've been told not to be trapped into playing from root note to root note when jamming, learning or improvising, but to learn to play BEHIND or in FRONT of the root note. Does anyone know what this means? Is it even a real thing?
Typically the terms "behind" and "in front" or "ahead" are in reference to the timing of notes. Playing behind the beat — playing a note or notes minutely later than expected — gives a feeling of relaxation, while playing ahead or in front of the beat — playing minutely earlier than expected — gives a more driving feeling.
These terms are not generally used in relation to scales, but could reasonably be interpreted to mean including notes other than the ones in the scale itself — chromatic notes, also called "outside" notes.
It seems like the starting place for you will first to be to learn about chords: what they're called and what notes they contain. Once you begin to understand chords, you can also begin to learn how scales relate to chords. With that knowledge, you can examine the bass lines you've learned, comparing the bass line to the corresponding chords to discover which notes in a bass line are "inside" or "outside".
For more on playing in front or behind the beat:
- What exactly is the act of playing behind the beat?
- Projecting "Playing ahead/behind/on the beat " onto tangible concepts
For more on playing "inside" and "outside":
The terms aren't really much, if anything, to do with scales. They're to do with timing. 'Behind' or 'in front' with relation to the actual place where beats are.
Music has an innate timing (on most pieces), where every beat has its designated place as far as its timing is concerned. And often, considering beat one (the most telling beat), that's where a bass player will play (and is expected to play) a note - most often the root of that prevailing chord.
Playing 'in front' of that is often called 'pushing', and usually happens on the last part of the previous bar - the beat/note is pushed so it arrives sooner than expected. It gives a sense that the music is moving faster than it normally would, of course it's not, but playing on the & of 4 of that previous bar makes it seem so.
Not to say it always works! If the bassist does it alone, it sounds more like he's racing. It needs there to be there too, notably the drummer, the rest of the rhythm section, and often the vocals. The Beatles used this ploy quite a bit.
Playing 'behind' the beat is a little less usual. It gives a feeling of 'laid-backness', relaxedness. Personally, when I do this, I'm playing two notes - on the beat and directly after it, 1&, often with 1 being 'ghosted'.
Keep going with the scales, and just as importantly - maybe more so - arpeggios, as they are the mainstay of most bassists playing.
EDIT - due to Elements in Space's comment, it occurs that perhaps OP doesn't mean 'rote' at all - rote taken to mean written.
If it actually means 'root, then that elicits a completely different answer, where the terms 'before' and 'after' aren't particularly relevant - or accurate.
So, reading between the lines. Between may be more appropriate.
That would be use of passing notes. The notes which don't belong to the chord at that bar, but would usually be diatonic notes, but not necessarily so.
Let's take a simple example. Chord on bar 1 is C, bar 2 F. Instead of simply playing a C bass on bar 1 and an F note on bar 2, you could play C, D, E, E on bar 1, or C, C, D, E, leading directly to the F in bar 2.
Or, same scenario: C, B♭, A, G on bar 1, again leading to F on bar 2, this time in downwards direction. All notes 1 beat long.
That's got both stations covered. If the latter is what OP wants, please let us know by correcting the question, and I at least will expand on my answer.