Below is a list of papers and articles written about the EMPP and related projects. If I am missing something that should be here, please let me know!

Specifically about the EMPP:

P. Bloland. The Electromagnetically-Prepared Piano and its Compositional Implications, in Proceedings of the 2007 International Computer Music Conference, Copenhagen, Denmark, pp. 125-128.

E. Berdahl, S. Backer, J.O. Smith III. If I Had A Hammer: Design and Theory of an Electromagnetically-Prepared Piano, in Proceedings of the 2005 International Computer Music Conference, Barcelona, Spain.

N. C. Britt. Actuated Acoustic Instruments: Relationships and Mind-Sets, PhD dissertation, Princeton University, 2013.
(contains a section on the EMPP, along with analyses of some of my EMPP pieces)

S. Ricks. The Electromagnetically-Prepared Piano: an interview with Per BlolandSEAMUS News, Issue No. 2, Aug – Oct, 2013/14. (Not exactly a paper, but perhaps of interest)

Related work:

A. McPherson. The magnetic resonator piano: electronic augmentation of an acoustic musical instrument. Journal of New Music Research 39 (3), 2010, pp. 189-202.

A. McPherson and Y. Kim. Augmenting the acoustic piano with electromagnetic string actuation and continuous key position sensing. In Proceedings of the 2010 International Conference on New Interfaces for Musical Expression (NIME 2010), Sydney, Australia.

A. McPherson and Y. Kim. Toward a computationally-enhanced acoustic grand piano. In Extended Abstracts of the 28th ACM Conference on Human Factors in Computing Systems (CHI 2010), Atlanta, GA.

D. Overholt, E. Berdahl and R. Hamilton. Advancements in Actuated Musical Instruments. Organized Sound. 2011, 16(2). 154-165.

G. Shear and M. Wright. The Electromagnetically Sustained Rhodes Piano. In Proceedings of the 2011 International Conference on New Interfaces for Musical Expression (NIME 2011), Oslo, Norway.

K. Gartner. N. C. Britt: Presenting the EMvibe—An Electromagnetically Actuated Vibraphone. Percussive Notes – The Journal of the Percussion Arts Society, PASIC 2013 Preview Issue, September 2013, pp. 62-63.

C. Raffel , N. Kruge, D. Douglas, E. Berdahl, W. Ju. The Lattice Harp: A New Hybrid Instrument and Controller. Proceedings of the International Computer Music Conference, New York City and Stony Brook, NY, June 1-5, 2010, pp. 127-130.

D. Blackley. The Spectral Piano Project. MFA Thesis, Simon Fraser University, 2013.

(still in progress)