Barred chord is use in guitar. Say you play a Am fingering barred on the 2nd fret, you get a Bm chord. Think what i mentioned earlier is not really called a barred chord (or maybe it is

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Quoting from an interview with Jaco for the song "Portrait of Tracy"(finger as capo):
Everything but the Eb has a natural harmonic; you have to press down on the A string at the B note (second fret) and then you have to touch the string on top of the Eb.
If you don't have big hands you won't get this. You touch the string on top of the Eb or it's really a D sharp and you get the D sharp on top of the B. So it's like you're using your first finger as a capo. So then you get the D sharp and pick the open F sharp and B right from the D and the G string and you hit a low E and you also touch it a bit and you get a G sharp or a minor 3rd. So you've got the five, the nine, the three on the bottom, and a major 7th in the middle. And you've got the bass note because you're hitting the bass note and the G sharp.
For full interview pls read from
JacoPastorius.com : Interviews : Portrait of Jaco (1978)