Hi,
probably not suitable for what you want, but I've just started playing round with One Man Band & Busker software.

One Man Band loads jpeg file, ( scanned sheet music) Busker you type score, chords etc in. They scroll as you play using psr styles.
http://www.1manband.nl/whatsnew.htm http://www.1manband.nl/busker/index.htm


best wishes
Rikki