How does picking position affect a guitar’s sound? I can make some general observations – the strings are brighter near the bridge, and they can be more percussive near the neck – but I’m not sure how that translates to technique and performance. Do certain styles or techniques favor picking in different locations along the strings? Are there any significant differences I should be aware of for guitar versus bass, or electric versus acoustic? For example, does it matter if I pick directly above an electric pickup?
I think this mostly depends on what you like.
Here's what I do on my bass that has two pickups(neck and bridge):
- When I want a brighter sound, I pick (or play with my fingers) on top of the bridge pickup (and lower the volume of the neck pickup, so that my bridge pickup is louder)
- If I want a more bassy sound, I play on top of the neck pickup (and lower the volume of the bridge pickup, so that my neck pickup is louder)
- If I want a combination of those two, I play in between of the two pickups
- If I want to mimic the sound of the double bass, I play higher than the neck pickup; I play right at the end of the fretboard (this sounds better if I play with my fingers and not a pick)
This also depends on the instrument you are using. For instance, when I play with my (mexican :( ) Fender Jazz Bass (2 single coil pickups), I prefer to play on the bridge pickup mostly, but when I use my Warwick one (2 humbucker pickups), I prefer to play in between them, or on the neck one.
Picking directly above a pickup does mean that the harmonics that would be highest amplitude at that point are likely to be boosted (similarly, you can pick positions on the string that will reduce harmonics at pickup positions)
For a lot of my music I play positions from directly over the neck pickup to nearly at my bridge pickup (on a 2 pickup guitar) - this gives me a wide range of tones, and when I use heavy distortion, the effect on the harmonics is incredible, letting me choose anything from a 'chug' to a 'growl' to a 'squeal' etc. and that is before I even use pinch to further attenuate the low harmonics.
Yes, picking different distances from the bridge yields different degrees of acoustic response. The closer to the bridge, the "tinnier" the sound because the pick is not putting energy into the lower harmonics.
Then there are so-called "pinch harmonics" which are [typically, for me at least] created by holding the pick close to the tip and allowing the thumb to touch the string as well. As you move along the string, different harmonics will be emphasized.
And then there are true harmonics, which follow the same pattern as the opens strings, except that the "nut" is now where you've fretted the string. So count your typical 5, 7, 12, or more frets up from there. You can pick through a chord that way for a shimmering effect. Steve Morse does this frequently. There are different techniques for finger-picking and flat-picking in order to "touch" the harmonic as you pick the string.
What I've described above applies to both acoustic and electric guitar. As for picking directly over a pickup, I tend to avoid this simply for the fact that, depending upon the depth of your picking stroke and the height of your pickups, you may hit the pickup (or its cover) and interfere with your picking motion. For basic ergonomic reasons, I tend to pick between the neck and the middle pickups, unless I am intentionally seeking an alternative sound.