It depends, when I have more time and freedom I like to experiment with different instruments first and create the idea behind the music as I experiment, as long as it doesn't stray too far from the theme requested. But when there isn't much time or the request is more specific, I already plan what tone and instruments I will use beforehand, trying to streamline the process so I have more time to focus on the arrangement. For this jam, I did a mix of both.