How to measure change in emotional responses when pre and post tests use different measures?
Normally, I'd recommend using the same mood measure pre and post manipulation. This allows you to assess the size and direction of change. It also likely removes more error variance from the post-test measure (which would increase statistical power), because using the same measure is likely to increase the correlation between pre and post.

That said, if you've used different measures pre and post, then you could perform an ANCOVA with group as independent variable, baseline mood as the covariate, and post-test mood as the dependent variable. 

A slight possibility is that you could  map scores on both tests to a common scale. This might allow you to make qualified claims about whether emotions increased or decreased. That said, this would require that you have access to additional data on people who completed both tests in a non-experimental context. You could then use the means and correlations between the two tests to develop a mapping to a common scale.