I introduced the app Anytune in a 2016 post, and provided a link to my video demo. Subsequently, I wrote a complete "How to" article, accessible from the following links.
A version of this article was first published as Chan, M. J. (2017). Anytune slows down sound tracks for language practice. In M. O’Brien & J. Levis (Eds), Proceedings of the 8th Pronunciation in Second Language Learning and Teaching Conference (pp. 191-194). Ames: Iowa State University.
A version for CATESOL News Fall 2017 Vol. 49, No. 2 was slightly modified to fit that publication.