I had this tune in my head for years and could remember the line "I heard the sweet sound of a blackbird" but that was all and it should have been "voice". I kept playing the tune and asking my Folky friends if they knew it, and always drew a blank. No amount of googling helped either. Then my son (now 40) came to have a holiday with us here in Spain and when I played the tune, he remembered nearly all the words. He even remembered it was from an old Spinners LP that I had many years ago (I had completely forgotten).

Thanks to this thread I now have the words, and intend to play it at our little jamming session today, wife singing and playing guitar and me on recorder(outside a bar in the sun). Should be a laugh!

Thanks again and I managed to find this by googling as I now had more words especially "mechanical" which I had forgotten.