Music for Mood Manipulation
These are the three songs used in a psychological study about whether mood affects moral decision-making, which also involves a sort of horrifying theoretical scenario about a train.
A number of variables seem to be at work, but the songs were chosen to correspond to the following states:
Positive:
Neutral:
Negative:
The summary doesn’t explain why these songs were chosen (although it seems like the last two could be swapped), but the full study ($40) is here, and a general takeaway is to avoid footbridges that overlook trolley tracks.