I have a player who has a level in a prepared arcane class (wu jen from Oriental Adventures from 3.5E, modified to work in a pathfinder ruleset) and has decided to take a level in the Geisha Bard archetype from Ultimate Magic. She did this in part as a skill boost, in part for roleplaying reasons and just plain coolness, in part for the weapon proficiency -- she really wanted to use a War Fan without having to spend her feat on exotic Weapon proficiency -- and bonus feats, and partially to allow her to give an attack/damage buff that stacks with bless. It suits the character, who is the sort of person who likes to dabble in a lot of different things.
However, I'm a little unsure of how to handle a character who can cast both prepared and spontaneous spells. Since both wu jen and bard spells are arcane, one interpretation I can see would be that the character can now prepare any spell from the wu jen or bard spells that she knows as a prepared wu jen spell, up to her number of prepared spells per day per level, and cast any arcane spell she knows spontaneously, up to her number of bard spells per level.
I suspect this would be excessively powerful, however, and not what would normally be allowed.
Are prepared arcane spells with the same name as a spontaneous arcane spell the same spell? If she knows Sleep, for example, as an arcane spell, does it matter whether she knows it as a wu jen spell or a bard spell?
I am not familiar with the 3.5 stuff but does this class have a spellbook? if so then they have to prepare their arcane spells from spells within that book. It will matter which class casts which spell because of caster level and hence duration and other variables I think. Just run them as two different classes that run spells completely separately.
You keep track of the spells from different classes separately. Your spells known for one class are separate from your spells known from the other class, and vice versa.
Let's say we have a wizard that knows 5 spells and can cast 3/day, who has a sorcerer level and knows 2 spells and can cast 4/day. If his sorcerer spells are not also in his spellbook, he can't prepare them in wizard slots. Likewise, he can't use his wizard spells known to cast using sorcerer slots.
It's 2 different spell lists and two different mechanics. Treat them as such. It's like two different class abilities that do not interact with each other.
I thought as much, and this newly-trained geisha selected her spells accordingly, going for ones that were not available in her spellbook yet, or not even on her wu jen spell list. Wu jen do have spellbooks much like wizards, with a severely restricted spell list that I had to import a number of spells from the pathfinder spells into to keep the magic user from lagging behind.
Interesting effects come from spells on both class lists but at different levels. You have to indicate which 'flavor' of the spell you are taking and add it to the appropriate level slot of that class.
For example, take a player who is Paladin 6/Cleric 4. Lesser restoration is a Cleric 2 and Paladin 1 divine spell. You can put it into a level 2 cleric spell slot, or a level 1 paladin spell slot, but not a level 1 cleric slot. If you have brew potion though, you can brew the paladin version for less money and time.