It's not a dumb question. What this variation is called will often vary with the type 9r genre of music.It can happen in any style of music,modern or classical etc. And it can also be a melodic sequence a melody instrument, like a flute etc is playing, or even a rhythmic or harmonic deviation from the main body of the piece. And it can occur in other places in the musical piece, not just the end. In classical music, this change will usually be indicated with the Italian 'Ad Lib' notation. I t might be called something like "Theme and Variation(s)", like a famous virtuosic classical guitar piece called Variations On A Theme By Mozart.Modern music mayseem unstructured to some but it actually does have rules that define various modern musical styles eg Blues, Country, Pop, Rock, Metal, Jazz etc.Pop music is typically written to a formula or pattern of verses and chorus, with optional intro, bridge and outro sections in the song. The intro, chorus and outro and bridge sections are likely to grab listener attention so these are good places to introduce, repeat, emphasise and leave a lasting auditory impression in the listener's mind of the a important "hook" idea in pop music. The "hook" is the main idea the composer wants to get the audience "hooked on",what will typically allow the as ong to become a "hit", with everybody remembering this key, catchy little sequence. It will be different from the rest of the song's body because it has to be noticeable, stand out etc. The Bridge or Middle Section (can have slightly different names) will relate to the main concept of the song but it will typically restate it in a Dr ifferent way, so as to grab audience attention with such a change. Often, it is the chance for the lead guitar or other instrument to show off their skill with a solo. But sometimes it can also be a vocal Bridge, where the singer or even a choir does a variation to the main melody stated in the verse and chorus. One form it can take is when a song is cruising along, all nice and melodic and then it suddenly shifts to a section where the singer begins to "rap"or say a section. Rock singers sometimes do this, for emphasis. You hear it in Rolling Stones songs, some Beatles music, also sometimes in Elvis' songs, too. These variations avoid the listener getting bored, too comfortable with the main theme, or they are used for emphasis, to bring home a point, attract attention, leave a lasting impression, sell a concept etc. Or simply to show off musical skill, which you often see in classical and even Jazz and Blues music performance.It's interesting to analyse any musical composition, any genre/style to see how they do this, even in the good OLE country "Three Chords And The Truth" style, where the musical backing may suddenly stop and the singer(s) might just sing the lyrics a capella" style, which is an Italian musical terms that refers to singing like in a chapel choir, like "chanting" the lyrics.
