Adrian Alexander Mann created a piano with bass strings that are unwound and are at full linear length relative to the pitch they produce.

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David Klavins and his company Klavins Piano have created a model called the M450, which is a vertical piano that uses the function of gravity and the elongated string length to create a piano with enhanced and rich harmonics. Similar to the Alexander Piano, the M450 is an attempt to enhance the harmonics on the lower notes in the pianos register.

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Conceptual sculptor Bjorn Perborg built a 5 key piano as part of a gallery show, according to him the inspiration for the piano is “I showed an installation about the Collyer brothers, two hoarders who lived like hermits in Manhattan during the first half of the 20th century. One of the brothers used to be a concert pianist and I thought a crippled piano could go well with their story.”

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A Loja de Pianos constructed a copy of the 5 key piano, which is now owned and used by Fabricio André Bernard Di Paolo known on Youtube as Lord Vinheteiro

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Wayne Stuart and his company Stuart and Sons has released a piano called the Beleura which has a range of 108 notes.

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Invented by Geoffrey Smith the Fluid Piano features sliders located near the keyboard that allow each individual string on the piano to be microtonally retuned live while the instrument is being played. From the default central tuning each string on the fluid piano can be detuned down or up a half step, even allowing three adjacent keys to produce the same pitch or two adjacent keys to produce a pitches in reverse order to the rest of the piano.

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Another piano by David Klavins the Una Corda is a piano with only one string attached to each note. On top of that feature the piano has an open frame design allowing for a more open sound quality and a louder sound, given the sound is quieter then a typical upright piano because the Una Corda has less stinger per note.

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Several pianos modifications have been made to allow the piano to have sustain, mostly from electromechanical means similar to the ebow on the guitar.

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A mandolin attachment is a way of recreating the “honky tonk” sound found in parlor pianos from the mid 1800s. These attachments are used to modify existing pianos allowing it to be selectively used to alter the timbre of the sound.

John Kovac invented a keyboard attachment that converts the action of a qwerty keyboard into the relative locations of keys on a piano. ¹²⁾

William A. Sethares constructed a prototype of the Hyperpiano, a piano with the string modified to no longer be of consistent thickness, which each string having segments of thicker and thinner wire, which makes the instrument have a vastly different set of harmonics then a standard piano.

Percy Grainger created a 1/6th tone piano to use in his musical compositions.

Doug Blackley- Inventor of the Spectrumpiano.
Percy Grainger- Built a 1/6th tone piano known as the Butterfly Piano
David Klavins- Maker of experimental and expanded function pianos known for the M450 and the Una Corda
Sarah Nicolls- Builder of the Future Piano and the Inside Out Piano, she is interested in expanding the piano.
William A. Sethares- Inventor of the Hyperpiano.
Wayne Stuart- Maker of the Beleura a 108 key piano
Adrian Alexander Mann- Builder of the Alexander Piano, a piano with extended bass strings.
Bjorn Perborg- builder of a functioning sound sculpture that is a 5 key piano