Last game my group had a problem in that our characters had to roll to see if they could remember things and we couldnt find an appropriate modifier. Specifically we needed to determine if one character could remember details about a specific friend of that characters parents. That is, the characters parents had numerous friends but one of them turned out to be important for the plot and the story guide wanted the character to roll to determine how much info the character could recall.
second another character was presented with a song from their childhood and wanted a roll to determine how much of the melody, lyrics they could remember as well as the circumstances in which the song was sung.
We couldnt really find an appropriate ability to roll to determine whether or not the character remembered these facts. Are we missing something or are there anyone on this forum who has solved this problem in the past?
We though about using Concentration representing the ability to concentrate on navigating your own mind, but also Intelligence as a sort of fact recall or even Perception representing self-awareness. But none of these feel entirely satisfactory.
the same thing goes for willpower. We have a tentative idea that willpower is best determined by a Personality Trait roll. The characteristics feel very inappropriate and the same goes for any ability I can think of.
P.S: none of the characters in questing have the virtue "magical memory" or the ability to build memory palaces.
Checking A&A p.32 Memory: "The rational memory is the power of recollection, reminiscence, and active recall and is the province of man rather than beast.", an Int + Concentration rolls looks good for actively recalling something.
It would be different, if the one attempting the recall had tried to use TMRE p.25ff Art of Memory to actively memorize the item to be recalled before.
Best add an example for the kind of 'willpower' you mean: just everything covered by ArM5 p.49 Strong Willed of ArM5 p.61 Weak Willed? That would be a large area to be handled by many kinds of dice rolling. Suppressing distractions, praying, meditating etc. are covered by Concentration (see ArM5 p.82 box and RoP:TD p.36f, but also other places).
I would use Reputations mechanics (corebook, page 19). Set a base difficulty based on how close or lose the relationship between that friend and the character, then adjust based on that friend's reputation, and add a difficulty modifier if the thing to remember is obscure, if the character have a virtue or flaw that could kick in (Busybody is nice in these situations), pick a characteristic like Int or Per, and roll without any ability.
Anyway it seems one of these situations where the SG is going to do a lot of numbers to get an EF he could just guess. Also the kind of roll which seems to be a potential bottleneck to the narrative, because maybe the story plot needs the character to know the answer. Or it doesn't, so everything of this is just a waste of time. So why don't just give the character the information? There are already too many things to roll anyway. And if it seems just too simple, handle the players some NPCs and hints, and roleplay the memory.
I would tend to go for a pure Int. Consciously recalling something unconsciously remembered seems not to be a trainable ability to me.
The Art of Memory is trainable of course, but then the memorisation is a very conscious process.
When it comes to will-power, I think a lot of it is covered by personality traits. Strong- and Weak-Willed may modify your ability to overcome personality traits by force of will.
For willpower, in addition to Personality Traits and Strong/Weak-Willed already mentioned, we do also have this statement in the core book about Stamina:
Stamina (Sta): ...It is staying power, both mental and physical, and one of its most important components is simply the will to live...
For memory, you can maybe sidestep the issue with the CrMe guidelines in HoH:TL for refreshing memories on page 72/73. You can probably cast some useful spontaneous spells with a decent CrMe. You might also want to look at HoH:S, page 69 at episodic memories - there's a degree of success chart for creating memories that might be adaptable to help determine how much a mundane roll lets you remember.
Raw perception would be my call for remembering specific details. As someone said, you need to perceive what occurred, to have a chance of remembering them. Whenever possible, if I can find a non-int stat, that's the way I'd go, as int is such a go to stat. As it's a raw stat, with no skill bonus, just use a lower target number.
Also, one could spont an intellego mentem spell call it "Recall the lost memory" if the roll failed.