The term 'fifths, on musical scales' can be summarized as the interval of five notes in a scale. This interval is often referred to as a perfect fifth, and it is one of the most important intervals in music theory. The crossword solution for this term is SOLS, which is an abbreviation for the Latin phrase 'sol fa re mi'. This phrase is used to refer to the notes of the major scale, which are the basis for all Western music.