Here we use basically the same rhytmic pattern as 
"variation#2" playing the 2nd measure syncopation in 
the bass part.

You can also play the variation with an 8th note 
syncopation on the 1st beat (Figure 2).

Musical exemples. Example 2: You can also syncopate 
the first note of each new chord by an 8th note.


Example 3. This example is a transcription of the rhytm 
guitar part played by Toninho Horta on the introduction 
of the song "Aquelas Coisas Todas"  (Toninho Horta) 
as recorded on the album "Terra dos Passadors com 
Toninho Hortae Orquestra Fantasma" -- Terra dos 
Passaros 1979.
It's based on "variation#3", with a syncopated bass 
line.

To keep the samba feel and play the bass line at the 
same time, you must play the bass line with the thumb 
when it occurs as an independant line and with the 
first finger (index) when it occurs in a "lock style" 
situation