this song is number 4 on the "Purple" album, I haven't 
seen any really good tabs for
song's intro so here is one. this doesn't reslly sound 
good by itself but put it with some
& drums or play along with the song and you'll see 
that it's right.

bass plays for about 2 measures and then do a single 
downstroke on the D chord and rock
and forth on the wah-wah pedal and hold the chord for 4
 beats then start this.

--2-/-5-/-7-/-9----------------------| 
--3-/-6-/-8-/-10---------------------| 
--2-/-5-/-7-/-9----------------------| 
-------------------------------------| 
-------------------------------------| 
-------------------------------------| 

jsut keep the same shape and slide the chord to those 
spots. pressing down on teh pedal
each new chord. this is done a few times on the intro 
and during each chorus.