w:Jingle Bells, Or The One Horse Open Sleigh. Sung by the w:Festival Speech Synthesis System's "singing-mode", using the default US voice . Piano accompaniment by w:TiMidity/freepats. Source: [1]
I was given a text to speech program to play with and this is what i came up with using audacity and some sound clips/fx from the library. All sounds are free to use combined on open source software. Short ditty 1 minute.
A robot voice made with text-to-speech and voicechanger. Io. Sounds a bit like doctor who's cybermen (however, their voices were not made using text to speech back in the 60s/70s - they were made using an electrolarynx or vocoder.