Finding the Right Tempo for a Cue
Getting the tempo of a scene right is one of the most essential parts of film scoring. Even the best music can be a disaster when it drags a scene or pushes it too hard.
Often there are only few objective indicators to find a tempo and it has a lot to do with gut feeling. The tempo of cuts or any visual motion that gives a sense of musical tempo (e.g. steps) are a good first thing to look at and to get a rough feeling. In order to find the right tempo, you might want to lay a pulse against the pictures (maybe as simple as a repeating note) to figure out whether it feels right or not.
Also try slight changes and see how it influences the perception of the scene. In general, it is better to be a little too fast than being a little too slow. A slightly too fast tempo will give this edgy pushing feeling which is great for action sequences, a slightly too slow tempo will create a feeling of dragging which is extremely annoying and can take away a lot of tension from a scene.
So don’t just pick a tempo randomly that “seems about right” but try several ones before you actually decide to go for one.