Originally Posted by: ZozzieIt's where we change from one chord to another but in doing so we add a couple of single notes that link the old chord to the new one. And the last single note is usually (I think) the root note of the new chord.

As Jon mentioned, that technique is called walking bass. I cover the idea in these 3 tutorials to get beginners started on it:

http://www.guitartrick.com/tutorial.php?input=426
http://www.guitartrick.com/tutorial.php?input=427
http://www.guitartrick.com/tutorial.php?input=428

These tutorials are about walking bass lines, but applied to blues style:

http://www.guitartricks.com/tutorial.php?input=151
http://www.guitartricks.com/tutorial.php?input=274

And here is the technique in classical style:

http://www.guitartricks.com/tutorial.php?input=1031

Hope this helps. Have fun!