Outcome

For the example about beginnings, I chose the Star Trek (2009) Theme, found here:

https://www.youtube.com/watch?v=EO1FZEUbZJE

From time 0:00 until 0:38 the music starts as one soft melody, which, as the piece continues, gets more layers added to it that exemplify the expansion of range introduction concept by increasing the layers to higher and lower registers. The layers, starting at around time 0:18, also have a very noticeable increase in volume, as the introduction at time 0:00 is very soft, and by the time the main melody begins the music is very loud.

For the pop song example, I chose Pop 101 by Marianas Trench, found here:

https://www.youtube.com/watch?v=yBDNvlvR8vA

The introduction can be found from time 0:00 until time 0:16, and is characterized by the vocal tones and no lyrics, and ends with the introduction to the beat.

The verses can be found at times 0:16 - 0:48 , and 1:28 - 2:00.

As stated in the song, the pre-chorus is present at time 0:48-0:55, and 2:00-2:08.

The refrain can be found from 0:55-1:28, 2:08-2:40, and 3:12-3:44 (the third refrain happens after the bridge, not the pre-chorus).

The bridge is the section from 2:40- 3:12, which is markedly different form either the verses or the refrain.

The conclusion starts at 3:44 and continues until the end.

Conveniently, the lyrics to the song also point out most of these structures.