Townshend’s demo process for Who albums was quite robust. He’d have just about everything arranged, by himself, in demo form by the time the band went to the studio.
The Quadrophenia demos were previously only available via bootleg, but have since been officially released. (The songs “Anymore” and “Is It Me” never made it into the final Quadrophenia concept album, but elements of the latter were incorporated into “Helpless Dancer” and “Doctor Jimmy”.)
This is Pete playing every single instrument and singing every single vocal line.
He was 28 at the time, at the height of his powers.