David Ryan is a mathematician, music theorist and composer based in the UK.
His main musical interest is working with and exploring just intonation (JI). He developed rational comma notation (RCN) in order to provide a link between the mathematical domain of rational numbered frequencies and the musical domain of understanding music better through its notations.
Although RCN is not the only notation system which exists for free JI, it has some desirable properties:
- being able to use traditional note names like in scientific pitch notation, e.g. C4, G5, F#2, Bb7;
- higher prime commas describe microtonal alterations, e.g.   ;
- prime commas can be combined into a single rational comma for each notation, e.g.  =  * , [11/13] = /;
- it uses algorithms to assign all higher prime commas;
- RCN has a version for each algorithm (the author recommends a particular algorithm).