The term TRIO TREBLED is a combination of two words, 'TRIO' and 'trebled'. A TRIO is a group of three people or things, while to treble means to triple or increase by three times. Therefore, the term TRIO TREBLED can be interpreted as a group of three people or things that has been increased threefold. The crossword solution NONET (5 letters) is a musical composition for nine instruments or voices. Thus, the term TRIO TREBLED in this context could refer to a musical composition for nine instruments or voices that has been increased threefold.