Plenty of horn is a phrase that refers to the use of loud, blaring horns in music or other sound production. The two crossword solutions for this term are TUBA and KLAXON. A TUBA is a large brass instrument that produces a deep, low-pitched sound. It is often used in orchestras and marching bands. A KLAXON is a type of loud, piercing horn that is used as a warning signal. It is commonly found on ships, trains, and other vehicles.