This paper presents a novel algorithm for the signal modification component of concatenative text-to-speech systems. The algorithm described here is based on the LPC analysis/synthesis framework, and achieves prosodic modification by time-domain processing of the LPC residual(LF-4 model). This method is based on a source-filter model. The proposed method achieves high quality prosody modification, retains the characteristics of the donor speaker, allows for spectral manipulation, and yields compact acoustic inventories and improved voiced fricatives.