The symbol X indicates that a ghost note is to be used. A ghost note is where the note is 4muted, with the right hand.
Bass Part - This bass line introduces 'ghost notes'
Drum Part - Quarter note triplets only are played on the ride cymbal in this example.
Bass Part - This example uses a number of previously covered concepts.
Drum Part - A tom-tom is incorporated into this pattern.
Bass Part - This example uses a number of previously covered concepts including an anticipation on beat '4 a'.
Drum Part - The hi-hat part is quite complex in this example and uses hi-haf openings and complex rhythms to create interest.