Heavy metal and Plainsong

Heavy metal noun - A metal of relatively high density (specific gravity greater than about 5) or of high relative atomic weight (especially one that is poisonous like mercury or lead).

Plainsong and heavy metal are semantically related in harmonized topic. In some cases you can use "Plainsong" instead a noun phrase "Heavy metal".

Plainsong noun - A liturgical chant of the Roman Catholic Church.

Heavy metal and plainsong are semantically related in harmonized topic. You can use "Heavy metal" instead a noun "Plainsong".