i think it is

a) form - open, sensorial, a similar openness to music in that there are no 'fixed associations' (Langer, Form and Feeling)

--> this form opens up associations and an emotive engagement

--> which gives the audience a certain experience and this experience differs according to memories and emotions activated in the audient.

So according to this theory, changing the form changes the engagement. But i guess that is always the case.

Hmmm.

essentially I am interested in the 'best' form to illicit memories and feelings aligned with similar notions of feeling and music and langer purports.

Ahhhh research. How mad your drive me with your quicksilver nature and your shape shifting appearance.

And all the sitting still is getting to me.