What does it mean to be a message-passing concurrent language? This work attempts to build a framework for classifying such languages by judging four in regards to features and performance. Features of process calculi are used to evaluate Go, Rust, Erlang, and occam-π. Furthermore, standard communication time, selection time, and multicore utilisation are examined. Although each of these languages use message-passing concurrency, their approaches and characteristics are different. We can start to build an initial classification based on message-passing type, language support, and feature support. Such classification allows an initial discussion of the suitability of the evaluation framework, whether it is useful, and how it can be expanded. Approximately 50 further languages have been identified as potentially supporting message-passing concurrency to further build up the classification.