The term 'Hecklephone Relative' is a crossword solution that can be filled in with the word 'OBOE', which is a four-letter word. The OBOE is a double reed woodwind instrument that is part of the larger family of woodwind instruments. It is similar to the Hecklephone, which is a type of OBOE that was popular in the early 20th century. The OBOE is known for its distinctive sound and is commonly used in classical music.