Problem:
Random songs gained from taking bard levels tends to be a problem when using -relevel. With frequent updates, some of which affecting bard builds indirectly. Its random each time and can be annoying when a song/curse you like is randomly learned thru the levels.
Without a "full" bard song/curse list you'll be at the mercy of RNG when you relevel, you can do relevel several times to force it to give back the song/curse to you. But it just takes too much time as these songs are learned at 10, 20, 30.
Worse still is if you have Dirgesinger, and you have "full song/curse list" but one of the songs is learned this way. As DS you get Reposeful Requiem as bonus curse at DS 1. If your 10th bard level is before the 1st DS level, and it gives you reposeful requiem as bonus at 10th, you're going to end up a song short.
Proposed solution:
Lock it in, just like how ranger's bonus favored enemy is locked in.
Or you could just add skill focus: perform on 6th bonus feat of bard so their DS levels dont give them that much RNG, only learning curse song as you take the 1st DS level. This solves the DS issue, but not the "early" low to mid level bard problem of mixing up their songs on relevel without a full list.
Note: Its not a problem that cannot be fixed by the player themselves, but bruteforcing thru relevels is rough. It is also open for exploit (2 bards get together... relevel several times to get rando song each time and then teaches each other "new" song/curse, rinse and repeat till the list is full.)