The Muse synthesizer-sequencer-instrument made by Triadex of USA. This device was designed by two MIT professors (Marvin Minsky and Edward Fredkin) and first marketed in 1972. Less than 300 of their devices were made primarily to be sold in high-end audio stores. They were sold for about $350 in the 1970s.
The Muse is a music composer computer that is both a synthesizer and a melody composer. With the user-operated controls, it allows the possibility of over 14 trillion note combinations.
The controls are as follows: The four sliders in the lower left control volume, tempo, pitch, and fine-pitch. The switches on either side of the four sliders are used to start and stop the sequence or to step through the sequence note-by-note.
There are eight longer sliders on the right. Four of those sliders control the musical intervals (labeled A, B, C, and D), and four control the theme (labeled W, X, Y, and Z).
In the lower right corner are two switches. One allows the user to substitute a rest for the lowest note and the other switch provides for using an external amplified speaker. The tempo clock can be slaved to that of another muse which would allow for multi-part compositions. The device has a built-in speaker for monitoriing.
This Muse is currently for sale and can be bid on now via the Ebay Auction