As you see in the movie, Abby is soliciting audience participation. One of the sounds, HA, Abby has the audience make comes from Mulan's martial arts class:
In general, what Abby is acting out comes from the movie Mulan II, and one needs to be familiar with both Abby's methods and the movie to catch them. However, after watching this Abby movie with Jane, I have learned that that there is more.
When Abby is making rowing motions and singing "Just around the river bend....," she is playing Pocahontas. Toward the end of this little movie, when Abby says: "SING!" and is singing AH AH AH scales, she is acting out the scenes in the Disney movie The Little Mermaid where Ariel trades her voice for legs.
The actual Abby movie is a 10 minute quicktime movie. The file size is 118,224KB. Left click on two scenes below start the movie playing or right click to download and then play. Because of its size, this Abby movie may take considerable time to start playing or to download.