These are the audio files for Sing a Rainbow. Download the file for your part, plus the file that is just called Sing a Rainbow, which has all parts.
An MP3 player should recognise the files as being part of an album called MCC July 14 with artist Medina Community Choir.
In terms of instruments used, sopranos are violin, altos church organ, and bottoms bassoon. The sound is also panned in the stereo field, so sopranos and bottoms are fully on the left side; altos fully on the right side.