
BillyGoat |
I'd definitely allow players to use the appropriate Perform sub-skill. After all, especially in a renaissance or medieval setting, a large part of a successful performance is the ability to improvise off of a substantial library of memorized pieces.
Alternately, if someone wanted to represent a broader ability to craft song/story/play, without necessarily having any talent at acting or singing, I'd allow a Profession (Composer) sub-skill.
If it ever mattered, I'd look at setting different DC's to accomplish the same task between the two, with the Profession being at a (slight) disadvantage to the Perform skill. The theory being that someone who is skilled at acting is probably going to have an easier time putting together a script, since they're intimately familiar with the demands/nature of stage and a broad selection of existing plays.

littlehewy |

I'd generally agree with the above, except to say that Profession (Composer) should actually have an easier time of it than the Perform subskill, for two reasons:
1) If someone is spending points on Profession (Composer), the only thing they can do with it is compose stuff - it would be punishing to those buying it if it was harder, but may actually entice those with Perform to spend skill points on the Profession subskill if it makes it easier.
2) As a performer and composer myself in real life, the skills are actually very different, and while learning to perform at a high level imparts the ability to compose, those that specifically study composition are, generally speaking, much better at it than those that have only studied performance.
I would make DCs for those with Perform only at least 2 (but probably 5) higher than those with the specific Profession (Composer) skill.
That said, the best way for those that aren't really interested in too much complexity on such a trivial part of the game could just equate the two - leave the Profession skill for those that can't perform.
Hope my opinions are useful in some way! Any more questions about music/arts, feel free to ask me :)
Edited to make more sense

Chemlak |

Profession (Composer) and Profession (Playwright) are perfectly reasonable.
Likewise, I'd probably let someone with Perform make checks for writing new material, but I'd put the DC up - just because someone knows how to act, that doesn't make them any good at inventing plots and dialog themselves. Just because someone can play the guitar doesn't mean they can write songs for Status Quo.
I'd probably let them use Aid Another on themselves (aid self?), though, if they have both skills.

BillyGoat |
In re-reading my own thoughts, and reading over littlehewy & Chemlak, I agree with their take of making it easier for the dedicated composer (both from a rules-benefit perspective and for "simulation accuracy").
EDIT
The old skill synergy rules from 3.5 would be helpful here.
While I understand the reason for removal (it was thoroughly cheese-able), I do so miss that in instances when it wasn't being abused.