Sequential Circuits Prophet-5 and Prophet-10 synthesizers from page 9 of Contemporary Keyboard magazine June 1978. This was the first Prophet ad to appear in CK, running during the first half of 1978, ending in July. It would be another four months before another SCI ad (Prophet-5!) would appear in CK. This ad features content about both the Prophet-5 and -10. The first versions of the Prophet-5 and -10 looked virtually alike. The more commonly known double-keyboard Prophet-10 didn't come out until 1979.