I have been working on this for a while, using Sopranotron for the Backing vocals.
Sopranotron is an iPad app which simulates a Mellotron using tapes recorded by the soprano Caitlin Downie. It does a lovely job, I hope you agree, in providing Ooohs, Aaahs, Eeeh’s and Baas, but I wanted to add some spoken or sung parts without singing or speaking them myself.
I couldn’t find anything on-line to do the job, and tried Siri but it was cumbersome and limited. However I found that IOS app developers could use the text to speech capabilities of Siri from within their programs.
I have almost finished the development of an iPad app that accesses all the available voices used to drive Siri. The access given allows quite a bit of control including raising and lowering the pitch and rate of each section of speech. I found that by splitting sentences into words, and words into sub-words I could add a bit of tonality into the spoken text. This is especially effective in the female voices and those in romance languages. Of course not all words work in all languages and the speech processor resorts to spelling some words, but you can fiddle by changing the spelling to drive a particular language to sound as you wish. You can also get fascinating sounds that aren’t recognisable words, especially from the oriental languages.
Having got my phrases as good as I could, I imported them into Logic Pro X and used the Audio Processing tools there to fine tune them and give them a bit of gloss.
I haven’t got a name for the app yet but it’s on the website as Tune-O-Vox until I can think of a better name which, to be quite candid, shouldn’t take long.