A swing rhythm can be created by tying together the first and second notes of an eighth note triplet. Play exercise 20 which contains triplets.
Now play exercise 21 which has the first and second notes of the triplet group tied. Do not pick the second note of the triplet group. Pick the first and third notes only. This gives the exercise a swing feel.
The two eighth note triplets tied together in exercise 22 can be replaced by a quarter note.
To simplify notation, it is usual to replace z with 6, and to write at the start of the piece,6=z illustrated below in exercise 23.
Exercises 21, 22 and 23 sound exactly the same, but are just written differently.
On the recording there are three beats to introduce this song.