Multiclassing And Variant Classes
Multiclassing between variants of the same class is a tricky subject. In cases where a single class offers a variety of paths (such as the totem barbarian or the monk fighting styles), the easiest solution is simply to bar multiclassing between different versions of the same class (just as a character can't multiclass between different versions of specialist wizards). For variants that are wholly separate from the character class—such as the bardic sage or the urban ranger—multiclassing, even into multiple variants of the same class, is probably okay. Identical class features should stack if gained from multiple versions of the same class (except for spellcasting, which is always separate).
Combine Songs (Ex): A seeker of the song of 2nd level or higher can combine two types of bardic music or seeker music to provide the benefits of both. The seeker chooses two music abilities and activates both using the same standard action. If either or both require concentration, the seeker can maintain concentration on both by using one standard action each round to concentrate. The normal stacking rules for bonus types apply to music abilities combined with this ability.
Combine Songs (Su): A war chanter of 5th level or higher with 12 or more ranks in any Perform skill can combine two types of bardic music or war chanter music to provide the benefits of both (normal stacking rules for bonus types apply).