In 1979, Roland released a monophonic version of the Jupiter-4 called the Promars. The Promars did not have the arpeggiator and the chorus effect, but introduced a second oscillator. It had the memory and preset selection buttons above the keyboard, which were less clumsy to use than those on the Jupiter-4. It also had 37 keys, making slightly smaller than the Jupiter-4.
The Promars was used by Depeche Mode (around early-mid 1982), Vangelis (early/mid 1980s), The Enid, Jethro Tull, Landscape and Spandau Ballet (synth lead on 'To Cut a Long Story Short').
Read more about this topic: Roland Jupiter-4