The P Bass is one of those things that Old Leo got right the first time.
The Precision Bass. He even got the name right. One of the best instrument names
of the 20th century. And one of Leo Fender's proudest achievements.
The Fender Precision bass changed the face of many kinds of music: Pop, Country, Blues, R & B
and even Jazz to a certain extent. The design has been copied by many different makers, but
it has not been improved (much).
When the P Bass was designed, nobody thought much in terms of tone shaping. (for bass)
It was just bomp baba bomp ba bomp ba bomp bomp... But once that sound was established coming
through the Fender Bassman (which was a revolutionary combination, let me tell you)
the electric bass took its place in the mix with authority, and the bassist stood in a position to
lead the band. Not all did, at least overtly. But the position is there, thanks to the P Bass and
the Fender Bassman.
Then players began to think of what else might be done.
So the Fender Jazz Bass was conceived... not as a replacement for the P Bass, but as a glamorous
younger sister. Fender built and sold them side by side, and has all along. In the sixties, the
controls and the two pickups on the J Bass gave the instrument more tones than the P Bass could
offer. So a more melodic bassist could put that to use. But sales of Precision basses never faltered.
The P Bass does one thing really well, and for many bands and many bassists, that's all they require.

All the hurriers and the worriers can play lead guitars, or shriek their fool heads off, or bounce harmonicas
off the back wall, or play a stack of keyboards three deep, but the bassist with the P Bass will bring
home the ship.
And these days, the difference between the tones of the Jazz Bass and what can be done with a P bass
are almost negligible. We have so much tone shaping control at our toe tips that the good old Precision Bass
doesn't have to be a one trick pony any more. Insert the great sound of those split Fender pickups into the
signal chain of your dreams, and shake the earth. I'm not saying that the Jazz Bass is irrelevant, because
that's my first love. I'm just saying that the P Bass gives up nothing. And gets the job done.
I will admit that several modern innovations have altered the game established by the
Precision bass. One of those is the five string, and the six string behemoths. Those do offer
something more. I admit. But lots of bassists like me will say quietly to themselves:
"IF YA CAIN'T DO IT WITH FOUR, YA PROLLY CAIN'T DO IT WITH SIX..."
Another really nice innovation is the PB & J Bass, with its excellent combination of tones.
That's a melding of the two worlds that ends up being a very useful instrument to play.
And one more of course, is the lightweight models offered by Yamaha among others.
I'm for that. I'm used to shouldering my nine pound Fender Jazz, and always considered it
part of the job, like carrying heavy amps. But a lightweight bass can still shake the earth
properly IMHO, so it's a welcome addition to the banquet of choices spread before the
modern bass player.