Morning Don
Since I changed over to backing track's I have obtained them from various sources.
Mp3 files £1.50 a track, with or without backing vocals from:
http://www.karaoke-version.co.uk/Midi files free from:
http://efmidi.com/I've got quite a few from You Tube, I use "Freemake" to convert to MP3 files but sometimes "Freemake" won't work so I record the You Tube audio using my Zoom and convert the Wav file to Mp3 with "Audacity"
Either way it doesn't cost a fortune and in most cases you can find a track which sounds decent.
I've uploaded a couple of example's from the Karaoke site, one is a song I'm working on "When you were Sweet Sixteen" by The Furey's great Banjo solo. The other is the track for "There goes my Everything"
If I need to change the key I use Audacity it does a pretty good job if you don't have to shift the pitch to far. I found when doing a pitch change on Audacity you have to input the original key and the new key, If you omit the original you get garbage.
https://app.box.com/s/2mchvr8s5sort74kszfh4lfmxw8e0vauRegards
Col