The dataset IDMT-PIANO-MM includes a total of 432 piano recordings (around four hours), which cover nine music pieces recorded in eight different rooms using six different recording devices. The pieces cover classical music (B. Bartók, W. A. Mozart, J. Pachelbel, and L. v. Beethoven) as well as jazz (S. Joplin as well as own compositions) and range from simple to medium difficulty. All music pieces are in the public domain. The recording locations range from small rooms to a large lecture hall. Information about the room geometries, piano position within the room, as well as wall materials are documented. The rooms include four different grand pianos, three upright pianos, and one stage-piano. At each location, audio recordings were made with three mobile phones (iPhone 6S Plus, Redmi Note 8, LG G6), two tablets (iPad Air 2, Amazon Fire tablet), and one stereo setup using two high-quality Oktava MK 012 microphones in an AB recording setup.