Sure, you could make up a song on the fly. In fact, the improv practice could benefit you in the long run! The difference however between that scenario and communicating, is there isn't much psychological pressure or trigger to not perform or get your message across when it comes to singing. You can sing with any word, sentence, (i.e. force all your sentences to start with vowels and avoid names) or even another language of your choice; the listener is only expected to be entertained as opposed to understand what you're saying.   Regarding the blood flow study, since we're both not neurologist, I agree with you that the researchers that are operating heavy magnetic machinery to scan brain activity have a some sense of what they're doing. My side of the debate is, despite all off their current knowledge of neurology, their studies are incomplete until we fully understand the power of the subconscious mind. Since placebos have been long proven to cure disease or conditions by suggestion or tricking the subconscious mind to do something, it may be directly physically causing an area of the brain to lack blood flow. An [article] (https://www.cbsnews.com/news/stuttering-brain-mri-study/) that describes the study also discusses the default-mode-network, a primary candidate of subconscious actions. That said, I'm not debating a lack of a neurological factor, only that psychology has a significant part it.   I share a similar experience of unexplained blocks coming at very random moments. It came suddenly at the age of 8, and has persisted since. And rather frustratingly, different severity levels with different people.   If you haven't heard of a good psychological theory, here's one of my favorites, from Bob Bodenhamer: I have a Voice: How to Stop Suttering. The theory goes that stuttering is embedded from one or two childhood moments where imperfect speaking was frowned upon. That in turn created a subconscious pattern to avoid situations that perfect speech is perceived as a requirement. As a poor compromise, a PWS ended up by creating avoidance strategies to not re-live that moment. The avoidance can take physical form (i.e. throat involuntarily blocking) or a mental one (by experiencing an instant panic attack or adrenaline fueled fight/flight response), The cure is to go back to that childhood moment, use NLP techniques to re-associate that initial feeling that speech has to be perfect, and handle imperfect speech like everyone else. I may not have done the best job of summarizing the book, but would highly encourage reading it if not done so. It does a great job at theorizing why stuttering is purely a psychological problem rather than a neurological one.