I could've gone for the easier example here with the official fighting game spinoffs but Touhou 9: Phantasmagoria of Flower View is one of the rare times the main shmup games of this series gets to have its own pre-battle themes, and I feel that because of that it takes a pretty interesting take on the kind of theme you'd expect.
The first pre-battle theme, is a rather pensive, calm yet tense piece, which permeates all pre-battle dialog sections before actual fights. While the game lets you skip these almost as fast as they appear, it would be a shame to because theme itself is rather beautiful. It takes the main theme of the series ("Theme of Eastern Story") and takes in a way that gives it some tension. Honestly, it is a really nice track personally, and that it is weird why such a long theme like this is relegated to just pre-battle.
The second theme, in stark contrast, has an incredibly short loop, and is used for the pre-battle dialog before the last boss of the game. This theme is really short, probably one of the shortest themes the series has ever had to this day. Despite this, it still manages to give off a sense of finality, that the final moments are about to begin, as if the theme itself is making you rush into action. It isnt as grandiose as a theme, but it has a pace to it that makes you want to go for it, even after all battles before it.