dont have a radio on the yard any more, but years ago, when Chris Moyles did the afternoon show on radio one he used to do this thing called 'Mystic Horse' (dont ask, cant even remember what it was about!) and he would play the sound effect of a horse whinnying - and my old mare used to answer - was quite cute, she wasnt ever upset or bothered by it but would stop eating her haynet and answer and then go back to eating!
I read a study (I think it was a university in Switzerland) that decided that Enya was the favourite with the horses they were looking at (based on heartrates etc).
(I just have my MP3 player on shuffle with travel speakers - he mostly ignores it but will look up in surprise when it jumps from a classical piece to Eminem!)
I had cool fm (belfast station) on in the car yesterday (Had horsey standing outside while I groomed). I think he was a little confused as to where all the voices were coming from! He started blowing on the car and snorting like mad! Then he just started walking away...so I turned it off
My girl is a stressy sort and if in the mood she only likes Classic FM, but not if the music is too BUSY, she likes very quiet relaxing, or... if cd is on, it has to be Enya.