Final answer:
The songwriting technique that is not recognized as a conventional method is 'fill in the blanks,' while 'matching,' 'use of themes', and 'brainstorming' are common methods used in crafting songs.
Step-by-step explanation:
Among the songwriting techniques listed, fill in the blanks is not recognized as a conventional songwriting method. The other options provided, such as matching, use of themes, and brainstorming, are common techniques used in the process of writing songs. Matching typically refers to the pairing of lyrics with melody or chords. Use of themes involves the incorporation of specific recurring ideas or motifs throughout a song to give it cohesion and depth. Brainstorming is an important initial step where songwriters generate a variety of ideas, which can include lyrical concepts, melodies, harmonies, and rhythms, before refining them into a finished song.