Birding app recommendations.

I have been reading the numerous posts regarding birding apps but wanted to get recommendations from other users. I thought that the Birding by Ear system was available as an app for iOS; but I couldn't find it. I have the Peterson Field Guide for Birds of North America, which contains the name of the birds and then their songs. That's what I had in mind for an app, nothing too difficult or with a lot of useless features to a totally blind person. I mainly would like to refresh my memory on all of the bird songs. I am using an iPhone 5 with the latest update. Thanks for any helpful information. There are so many bird apps and some of them are quite pricey. I would rather get some responses before I purchase one. Jo Anne Stombaugh