IPA Zounds is a sound change applier: a program that models linguistic sound change by applying sound change rules to a list of words. It uses a binary features model of the IPA, allowing users to write words and rules using IPA characters and the distinctive features of the model.
So, for example, a rule to lengthen any vowel before a final voiced postalveolar fricative would be written as:
[+syllabic]/[+long]/_ʒ#