A Federation-area species noted for their ceremonial rhythms, which Riker taps out through Ferengi interference to tell the Enterprise where he is being held in Ménage à Troi.
The Algolians are a humanoid people who appear in the Next Generation episode Ménage à Troi. In 2366 the Enterprise attends the closing reception of a trade agreements conference on Betazed, where an Algolian musician plays the traditional ceremonial rhythms of his people on a set of chimes.
The music becomes important later in the story. Riker, Deanna Troi and her mother Lwaxana are kidnapped by the Ferengi DaiMon Tog, and Riker gains access to the Krayton's communications system. He cannot send a clear message, so he alters the ship's warp field static to pulse in the pattern of the Algolian rhythms.
Wesley Crusher recognises the beat in what had seemed to be ordinary subspace noise, which allows the Enterprise to track the Ferengi vessel.