With over 50 apps in AppStores and several customer projects (Nestlé, Axa, Merck) I consider myself as expert in iOS and Android development. Please search for DSW Dev in iTunes AppStore to see my apps and also notice that I am not fixed on any kind of app.
Your requirement to have a app that can download the 42 audio files is feasible and can be done in very short time. There are two ways to do this, one is, once when the user install the app, a message indicate that he need first to download the files, all or selective (this could be a nice option). The other way could be to include the 42 audio files in the app and when installed, they are directly available to play.
In any of these two options, it is important to mark all 42 files (and maybe more in the future) to exclude them from the iCloud backup, if this is not done, Apple will reject the app, because the rule say that only data that the user creates with the app, should be backuped. As these files can be downloaded any moment, they should not be backuped.
It would be also nice to have a description and classification for the audio files, so that the listing showing them could be searched, filtered or grouped by this.