Entering an already crowded market, Symphony has announced it will produce an iOS app for its cloud-based messaging service.
The iPhone app will be released next week and an Android beta app is planned for the Summer.
Its main competitors for both web and app-based secure messaging are Slack and Bloomberg's Terminal.
Ironically, Symphony's greatest asset may be the fact that messages can be stored and accessed by a government agency: the law requires that financial institutions are auditable and their employees' communications be accessible in the case of an investigation.
Symphony was launched in September last year and is aimed squarely at Wall Street, posing a direct challenge to the ubiquitous Bloomberg Terminal.
Symphony was set up in 2014 by Goldman Sachs and 14 of the world's biggest banks in response to the news that some reporters from Bloomberg's news division had spied on the use of the company's business terminals by leading figures in the finance world.