Developer needed - Audio mixer/player

I landed here because I’m searching for a developer to develop a software and player (iOS/android).
So if this post shouldn’t be here please forgive me and tell me where can I find someone who could help.
I’m helping a Non profitable organization designing their site.
The site will be delivering audio files of the events that they organize.
These audio files are distributed according to the assistants language, so there are audio files in english (the language used by the speaker), and there are audio files for each one of the translations.
One thing I noticed is that they distribute the translations files without the sound of the original file, so it’s a little bit strange to ear only the translation. I asked why don’t they merge the original audio with the translation, and I think it’s because some people would prefer like that.
So, I remembered to make a simple software that would “merge” the original audio file with all the translations available and the final result would be a proprietary audio format that could only be listened using an player (this player would exist for desktop, android and iOS).
In this player the user could select if he would like to ear the original sound or the original file+the translation (and which translation) or only the translation (and which translation).
So I need someone to develop a simple software to “merge” the audio files and export the final audio, and a player for desktop, android and iOS that the user could use to ear.

You might get a better response if you gave your post a more informative title - add something like "Developer needed: ".

You’re right. Thanks