This famous song has a traditional "melody line," as demonstrated in Exercise 57 of Progressive Blues Harmonica. However, as you have seen in Exercise 35, licks can be substituted for the silent beats to make for a somewhat more "personalized" or improvised solo.
To create a solo with an even higher degree of improvisation, notes from the appropriate scale (in this case, the Third Position Blues Scale) may be substituted for more traditionally used melody notes .
Improvisation is considered by many to be more of an art than a science. For example, if too many improvised notes are substituted for the standard melody notes, the song may be rendered unrecognizable. In a later book, the subject of improvisation will be covered in greater detail.
The following solo based on the melody of Saint James Infirmary is only one of a myriad of possible examples. After learning this solo, you may choose to attempt to insert improvised notes of your own. How many notes can be changed or added without losing the basic "feel" of the melody?