I would consider the Roland RE-201, also known as the Space Echo, to be a marvel of engineering and musical acumen alike. It’s a perfect example of what I would call a “holy grail piece of equipment;” a piece of equipment that is universally respected and its sound is often cited as the very definition of what it’s trying to achieve.
And then there’s Björk’s 2011 concept album Biophilia. By all accounts, this is one heck of a gesamtkunstwerk! The album was conceived and recorded between 2008-2011, inspired somewhat by the work of her environmental organization, the Náttúra Foundation, and explores the links between nature, technology and music. The album was also released on ten interactive mutimedia apps (one per song) that link the themes of the album to concepts in musicology.