Flats on a fretted Jazz bass.

[paul_5]

Jaco only needed Rounds...

[Misdee]

You've also got to bear in mind, modern amps and cabs can make any bass with flats sound different to the olden days when valves and boomy cabs were the only option. There's an awful lot of  hi-fi bass rigs about nowadays that can give a much more precise and detailed version of the flatwounds sound. That clarity, power and punch can negate some of the reasons why bassists ditched those strings in favour of roundwounds.