1. Chords - Wrong chords really grate on my ears.....
2. Choice of melody instrument - sometimes difficult when replacing a vocal with an instrument.....
3. Style - Often built-in or even other available styles, do not do justice to a song, so many times I make my own styles. 4 measure repeating styles get a bit boring after a while.....
4. 'Feel' - being an 'ear' player, I think that feel is a very important part of any performance. I've heard many players who can only read 'the dots', play very mechanically - every note exactly on the beat and exactly the length as written.
5. Melody - It's important to play the original melody, but it's also nice to have the freedom to improvise and add some 'colour' - even if it's only a few grace notes.......
6. Tempo - I like to experiment with tempos. A totally different tempo to the 'normal' can sometimes bring new life to a song.