Most of my ideas start as an iOS voice memo. I’ll periodically prune those and offload anything I think might have potential into a folder that I maintain and it acts as my idea pool anytime I need a part. I also have that folder shared with my vocalist, who will periodically shoot me a version of some riff with a vocal melody, and then things are really off to the races.
Software instruments have also been helpful in communicating guidance to other band members if I’m hearing a particular drum feel, or something needs to be in halftime, or whatever.
There isn’t much I enjoy more than finishing a tune I’m proud of.