Prototyping is one of my favourites and I found it to be very effective from all my methods when I have to discuss with Stakeholders and C level.
By watching users, a process flow, pain points, awkward steps and opportunities can be determined by an analyst for improvement.
Without knowing the expectations and goal of the stakeholders and users, it is highly unlikely to satiate them
Interface for any software product will either be human or machine. Integration with external devices and systems is another interface.
This type of market research is different from brainstorming in which it is a managed process with particular participants.