But when we consider movements up or down the aggregate demand curve

But when we consider movements up or down the aggregate demand curve, we’re considering a simultaneous change in the prices of all final goods and services. Furthermore, changes in the composition of goods and services in consumer spending aren’t relevant to the aggregate demand curve: if consumers decide to buy fewer clothes but more cars, this doesn’t necessarily change the total quantity of final goods and services they demand.
Why, then, does a rise in the aggregate price level lead to a fall in the quantity of all domestically produced final goods and services demanded? There are two main reasons: the wealth effect and the interest rate effect of a change in the aggregate price level.