Pianos, harpsichords and organs are suited for microtonal music insofar as the strings/pipes can, within limits, be tuned to anything desired.

In the case of harpsichords and organs, the probablity that tuning issues arise is even slightly higher than average since there is often "old" music (baroque and older, from the pre-well-tempered age) being played on them.

For electronic instruments (syntheszers), there is, in theory, absolute freedom for the pitches anyway - not in practice, though. But nowadays, many synthesizers have a built-in retuning functionality. A broad overview over the microtonal capacities of synthesizers can be found on www.microtonal-synthesis.com.

A side-remark: Synthesizers, even without retuning functionality, often have a special functionality that is principally also suited for microtonality: the modulation wheel. An impressive example of how to make microtonal music with the modulation wheel can be found here. This is, however, not a particularly easy way to do it...

Strategies for more than 12 tones per octave[edit]

A potential source for troubles is the traditional keyboard design, which is optimized for diatonic scales and 12 tones per octave.

For microtonal music with not more than 12 tones per octave, this is not such a problem - fingerings for non-standard scales can be learned. But it becomes a problem if you need more than 12 tones per octave, or even want a non-octave tuning, such as Wendy Carlos or Bohlen-Pierce.

There exist several solutions for this problem:

1) 12 Note Octave Scales[edit]

(Terminology from www.microtonal-synthesis.com)

Use several keyboards whose keys are slightly detuned against each other.

Advantages are that the keyboard layout keeps the familiar property that 12 key steps span one octave, and the pitches typically need only minor retuning. This is not unimportant for acoustical instruments, where we usually have physical limits to the amount a pitch can be retuned. For this reason, this approach is widely used, especially in the field of contemporary classical music.

The disadvantage is, of course, that you need several keyboards. In the case of acoustic pianos, this means in practice that the maximal number of pitches per octave you can obtain is limited - to the number of pianos you can put on the stage together... "Arc-en-ciel" by Ivan Wyschnegradsky, for example, a piece in 72edo, is written for six (!) pianos, and "Limited approximations" by Georg Friedrich Haas, in 72edo as well, needs the same number of pianos and moreover a whole orchestra...

Electronic keyboards sometimes have the possibility to play in "split" mode, i.e. the upper and the lower half of the keyboard can send to different midi channels. Some keyboards offer up to 4 split areas. In this case, you need only one keyboard - but you still have the disadvantage of having to jump between the areas.

12 note octave scales piano tuning instructions for 17edo

12 note octave scales piano tuning instructions for 19edo

12 note octave scales piano tuning instructions for 22edo

12 note octave scales piano tuning instructions for 24edo

12 note octave scales piano tuning instructions for 41edo

2) Full Keyboard Scales[edit]

(Terminology from www.microtonal-synthesis.com)

Tune each key of the keyboard to a different pitch. The pitches of the keys keep the property of being arranged in ascending order - but the octave pattern will be different, and there are larger amounts of retuning required.

Some synthesizers support this, but not all (see, again, www.microtonal-synthesis.com).

Synthesizers supporting only 12 note octave scales can be brought to support full keyboard scales with the help of the Midi Integrator software, or the alt-tuner software.

A possible "full keyboard scales" piano tuning for 22edo, mapping two keyboard octaves to one acoustic octave, is decribed in Paul Erlich's paper on 22edo, on page 11.

In the case of acoustical instruments such as pianos, tuning full keyboard scales may even require major changes in construction. It has been done, however, e.g. on the 16th tone (96edo) piano.

3) Dynamic Tunings[edit]

Some instruments allows their tuning to be changed "on the fly", allowing access to more than 12 notes, although not all at once. The main advantage is that the keyboard layout keeps the familiar property that 12 key steps span one octave. The main disadvantages is that certain melodies will be unplayable, such as a rapid passage using more than 12 notes.

For example, the Turkish kanun is a diatonic instrument like a hammer dulcimer, but plucked, not struck. Each set of strings has a set of mandals, a tiny lever which when flipped changes the length of the string and microtonally changes the pitch. It's analogous to the sharpening levers on the celtic harp, but there are mote than one lever per string, and they sharpen considerably less than a semitone.

The easiest way to experiment with dynamic tunings is with midi keyboards and software. Scala and Lil' Miss Scale Oven have limited dynamic tuning ability. Alt-tuner allows retuning of individual notes (choosing among various ratios or among various EDO degrees), modulating to different keys (either by a specific interval, or to a specific note, or to the current bass note), and switching to completely different tunings. All this can be done via keyswitches, foot pedals, the mod wheel, or any control that generates a midi signal. These midi signals can come from any midi device, such as a 2nd keyboard, or even the computer's QWERTY keyboard. Technique-wise, using keyswitches would be similar to using mandals or sharpening levers, and using footpedals would be similar to using the classical harp's pedals.

4) Get an alternative keyboard![edit]

This is actually quite an old idea, since in historical tunings of the pre-well-tempered area, there was a demand for differing between flats and sharps.

www.denzilwraight.com has some beautiful examples of historical harpsichords with up to 24 keys per octave.

A list of existing church organs all over the world with split semitone keys can be found on Ibo Ortgies' homepage.

In modern times, the idea of generalized keyboards has come up again. Generalized keyboards can host the same fingering for multiple tunings. See, for example:

Wikipedia article isomorphic keyboards

Wikipedia article on generalized keyboards

Wikipedia article on Bosanquet

Wikipedia article on harmonic table note layouts

Wikipedia article on the Wicki-Hayden note layout

Wikipedia article on Janko

For electronic music, there is meanwhile a number of generalized keyboards that are available or are soon to be available, see followng list.

List of available generalized keyboards[edit]

Product	Manufacturer	Layout	No. of keys
Terpstra keyboard	Cortex design	2-dimensional, hexagonal	280
Thummer	Thumtronics	2-dimensional, hexagonal	114
Tonal Plexus U-PLEX, Tonal Plexus TPX2, Tonal Plexus TPX2s	Hπ Instruments	2-dimensional, rectangular	422
Tonal Plexus TPX4	Hπ Instruments	2-dimensional, rectangular	844
Tonal Plexus TPX6, Tonal Plexus TPX6s	Hπ Instruments	2-dimensional, rectangular	1266
MiniMod	Hπ Instruments	Various (hexagonal, rectangular, 1-dimensional et al.) XXX	XXX
AXiS-49	C-Thru Music	2-dimensional, hexagonal	98
AXis-64	C-Thru Music	2-dimensional, hexagonal	192
Opal Chameleon, Opal Gekko	Opal	2-dimensional, hexagonal	192
Monome 64	Monome	2-dimensional, rectangular	64
Monome 128	Monome	2-dimensional, rectangular	128
Monome 256	Monome	2-dimensional, rectangular	256
Lippens Keyboard		Janko(2-dimensional)
Daskin 5	Daskin Manufacturing	Janko (2-dimensional)	203
Daskin 6	Daskin Manufacturing	Janko(2-dimensional)	244
Vertical keyboard (Elaine Walker)	Elaine Walker	1-dimensional, 2 tiers of keys (black/white), with customizable black/white pattern	61, 76 or 88
Metatonal Keyboard	Metatonal Music (Ron Sword)	1-dimensional, 2 tiers of keys (black/white), with customizable black/white pattern
ZB2 Z-Board	Starr Labs	2-dimensional, rectangular	288
Microzone U-648	Starr Labs	2-dimensional, hexagonal	288
Microzone U-990	Starr Labs	2-dimensional, hexagonal	810
Dualo Du-Touch	Dualo	2-dimensional, hexagonal