The term "sideways mustache" is not a recognized term or concept within the realm of music. It is possible that it is a colloquial expression or slang specific to a certain local music scene or community. Without further context or information, it is difficult to determine what a sideways mustache might refer to in relation to music.
A "sideways mustache" in music, also known as a "mordent," is a specific ornamentation technique often found in Western classical music. It involves the rapid alternation between a note and its immediately lower neighbor (or upper neighbor, in the case of an inverted mordent). A sideways mustache is typically indicated by a short squiggly line through the note or by the letter "M" placed above the note. The sideways mustache adds a decorative flourish to the melody and can enhance the expressiveness of the music.
I'm sorry, but there is no terminology specific to music called a "sideways mustache." It seems like it could be a term coined by a specific musician or a slang term used in a particular music community. To understand what it might mean, I recommend searching for discussions or examples from musicians, music forums, or social media platforms where this term is mentioned. By exploring a variety of sources, you may be able to find context or explanations that provide a better understanding of the term "sideways mustache" within the musical context you are referring to.
