I don't konw if Telstar by The Tornados was the first rock hit to come over to America from the UK, as I was a mere lad in England at the time. But the "organ" on Telstar was in fact a "Clavioline" which was a strange one-and-a-half or two-octave mini keyboard (monophonic, to boot) which was designed to attach to the front of a piano keyboard (the old joanna-basher in our local pub used to have one). I remember my Dad was willing to fork out 12 pounds (almost a week's wages in 1961) for a second-hand one for me. I didn't go for it in the end though, because it didn't have 'that sound' - I was just getting into Jimmy Smith at the time.