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-pi. 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 a the evaluation framework, whether it is useful, and how it can be expanded. Approximately 100 further languages have been identified as potentially supporting message-passing concurrency to further build up the classification.