Searching CGTalk, I found some threads about guitar straps in Maya.  As suspected, the solutions (even there) are complex.  The suggestion there is to use IK spline, joints, and clusters (?) with point constraints (for the ends attached to the guitar) or joints, weights, and hair with dynamics.

Guitar straps (and similar straps) seem to require consideration of their application.  In stills, you could get away with something deformed into the desired shape (just to look correct).  For animation, you need a rigged strap with all sorts of controls and dynamics to have it somewhat replicate reality during the motions.

For instance, if I were doing a still image in Cinema 4D, I'd model the strap  (or use a ready made model), apply either a spline deformer or add a string of bones with simple inclusion areas, and bend it into the shape that matches the look of being attached, slung, and taut.  If I were doing an animation, the model would be fully rigged and I might consider applying dynamics with proxy collision detection.

Since Poser doesn't have support for things like IK splines, point constraints, and other more complex CA controls, animation would probably be more likely keyframing poses to get the correct look.  Having not used Poser's dynamic cloth much, I'm not sure if variable stiffness could be employed to avoid wet noodle syndrome.  You can definitely use the player figure as a collision object for the shoulder and to avoid other player intersections.  But also attaching the ends to the guitar here seems like an order of complexity that Poser can't handle.  Hybrid dynamic/conformer still seems like a possible solution - but I'm not up on the techniques involved.

C makes it easy to shoot yourself in the foot. C++ makes it harder, but when you do, you blow your whole leg off.

 -- Bjarne Stroustrup

Contact Me | Kuroyume's DevelopmentZone