While I don't have the same experience, I regard what you say as fascinating additional information about the complexity of thought, rather than something needing to be explained away - and I suspect these differences between people will be helpful in figuring out how minds work.
It is no surprise to me that you have to adopt existing terms to talk about what it is like, as vocabularies depend on common experiences, and those of us who do not have the experience can at best only get some sort of imperfect feeling for what it is like through analogy.
I have no clue what this means as I don't understand what to what you refer via "sounds".
Are you saying you cannot tell whether you are thinking or talking except via your perception of your mouth and vocal chords? Because I definitely perceive even my imagination about my own voice as different.
I feel they must know the difference(and anyone would assume that) but will answer you in good faith.
I can listen to songs in their entirety in my head and it's nearly as satisfying as actually hearing. I can turn it down halfway thru and still be in sync 30 sec later.
That's not to flex only to illustrate how similarly I experience the real and imagined phenomena. I can't stop the song once it's started sometimes. It feels that real.
My voice sounds exactly how I want it to when I speak 99% of the time unless I unexpectedly need to clear my throat. Professional singers can obviously choose the note they want to produce, and do it accurately. I find it odd your own voice is unpredictable to you. Perhaps - and I mean no insult - you don't 'hear' your thought in the same way.
Edit I feel it's only fair to add I'm hypermnesiac and can watch my first day of kindergarten like a video. That's why I can listen to whole songs in my head.
