What is the organ/ keyboard sound often made in 70s (reggae) songs?

you can hear it at the start of this reggae version of rihannas unfaithful, it comes in just after the piano:
http://uk.youtube.com/watch?v=HpzWQ_geNy...
thanks a lot

The sound on the Rhianna track is Hammond (or more lkely Hammond sample), but the sound was actually improved upon by Roland on their D50 in the 1980s and this sound can be heard by Aswad when they had the hit with 'Don't Turn Around', which was a sort of Hammond with atmosphere. You can still find it on most Roland keyboards or at least create it by layering a couple of sounds.

it's a hammond organ, nice!

sounds like a church organ to me

Three seconds of that wonderful noise was enough to tell me that was the mighty Hammond C3 with a Leslie cabinet, which is a rotating board in front of the speakers, which is what gives it that distinctive vibrato sound.