To do a play-off system, often called “brackets”, we need to start with 64 which halves until only 2 are left in the “final”.
The trick here is to pair off items so the “best” of these plays the “worst”, giving advantage to the best to stay the best (in theory).
You will see this soon in the college basketball tournaments - 64 teams start the play-offs, being paired by conference and “standing”. (On my song list, you’ll see the song ranking and year.)
Aha! I get the elimination aspect of a bracket, and I know there are different ways of filling it, but it was mainly the reason that Round 1 differed from Round 2 that escaped me. Of course, having to start with a power of 2 makes perfect sense. Thanks!