The lack of architecturally-significant mechanisms for aspectual composition might artificially hinder the specification of stable and reusable design aspects. Current aspect-oriented approaches at the architecture-level tend to mimic programming language join point models while overlooking mainstream architectural concepts such as styles and their semantics. Syntax-based pointcuts are typically used to select join points based on the names of architectural elements, exposing architecture descriptions to pointcut fragility and reusability problems. This paper presents style-based composition, a new flavor of aspect composition at the architectural level based on architectural styles. We propose style-based join point models and provide a pointcut language that supports the selection of join points based on style-constrained architectural models. Stability and reusability assessments of the proposed style-based composition model were carried out through three case studies involving different styles. The interplay of style-based pointcuts and some style composition techniques is also discussed.