In this paper we propose a new analysis-by-synthesis algorithm for multipitch tracking. It uses spectral base components extracted from isolated piano notes to model a spectrum. The advantage compared to other signal-based algorithms is the application of musical knowledge for the identification process. The Pian- oTranscriber uses a limited set of the 88 musical notes of the standard piano. The extracted time series for all possible notes are used for a resynthesis step. Original and resynthesized signals are compared using an adapted onset-detection function. The PianoTranscriber was parametrized, optimized and evaluated using subsets of the publicly available MAPS-database. For the evaluation, the PianoTranscriber was compared to the state-of-the-art algorithm SONIC. The results show that the PianoTranscriber outperformed SONIC using base components from the analyzed piano and achieved similar results using base components from other pianos.