Group of four (7)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">group of four</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for quartet that I've seen before include "Group of four performers" , "Two violins, viola and a cello string group" , "Set of four people" , "Stringed group" , "like a string one?" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">group of four</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for tetrad that I've seen before include "Group or set of four" , "number of Gospel writers" , "quartet" .)