The singer worked with producer Steve Lillywhite on material in 2009 and 2010 which had a more electronic sound, but put the project on hold because it didn't sound right with the rest of the band, although she hopes it will one day be released.
She told Billboard.com: "I think that some of those songs aren't right for Evanescence. Some of the songs that we had at that time may be for a solo thing in the future.
"We really do have a lot of extra songs from that time and also songs that the band wrote together."
Describing the sound of the tracks, she said some were "stripped-down and acoustic," while others were made with synthesisers, rather than the operatic rock of her main band.
She added: "It wasn't like Evanescence music. I went through this big phase where it was more based on programming, and not about the band really at all - but when we went into the studio It just wasn't sounding right."
Evanescence's self titled third album is released on tomorrow (11.10.11).