[SF] Looking for an obscure 1970s science fiction novel — idiot savant flute player with a hidden genius inside novel from the 70's..

This has been bugging me for nearly fifty years. I read this book around 1976, borrowed from a friend, and nobody I've ever asked has been able to identify it. I've posted before without luck, so throwing it out to this community with everything I remember.

The protagonist setup:

The main character appears to be an idiot savant — a flute player — who functions at a low level in everyday life. The twist is that living inside this person's mind is a second, vastly superior intelligence that has deliberately withdrawn from ordinary human contact because it cannot tolerate the noise and limitations of average minds. The savant body is essentially a biological life support system that keeps the inner genius anchored to the world.

The plot trigger:

A crisis of cosmic or universal scale develops that requires the hidden genius to emerge and engage. This is what draws the inner intelligence back out.

The propulsion concept (this is the really unusual detail):

At some point a massive planet or planet-sized object is compressed/miniaturized down to roughly the size of a pinhead. This compressed mass is then attached to the bow of a spacecraft. The enormous gravitational/spatial distortion created by the compressed object warps space ahead of the ship, allowing faster-than-light travel. This is essentially a spacetime metric distortion drive — which was a remarkably ahead-of-its-time concept for 1976, predating Alcubierre's theoretical work by nearly two decades.

The distributed alien entity*:*

There is also a non-human being that communicates across lightyear distances. The entity's "head" or focal point exists locally, but its body or soul is somehow extended or woven across interstellar space. It's a distributed consciousness with a local interface node — not a telepathy-between-humans concept but something more exotic and structural.

What I don't remember:

The title, author, cover art, or length. It was likely a mass market paperback given the era. The tone felt serious and ambitious rather than pulpy — it had genuine ideas in it.

Why it matters:

This book genuinely influenced my own thinking and creative work for decades without my fully realizing it. Would love to finally give it proper credit.

Any identification appreciated — even a "this sounds like it might be adjacent to X author's style" would help narrow the search.