Always fascinated by the possibilities of alternative MIDI controllers with isomorphic key layouts, I’m increasingly interested in the LinnStrument from Roger Linn Design for use in xen-micro composition.
Nearly everything looks good about this controller and it’s really alluring considering the potential for expressive MIDI performance, and from what I’ve read, it would appear to be possible to make a few internal tweaks to the Xen-Arts VSTi, in order to make them responsive to the default MIDI CC pitch and timbre mappings that are a central feature of the LinnStrument.
Obviously, this is a controller that doesn’t have it’s own sound-generators, so to use it for playing microtunings, it must be connected to hardware sound-modules, or to a computer and virtual instruments which support full-keyboard microtuning; something in our world that is expected, understood and done as a matter of routine.
There are however some technical considerations in using this controller for serious xenharmonic and microtonal composition tasks…
Each row of keys plays an underlying chromatic scale of MIDI notes, and each of these eight rows can be offset by some interval, which, by default, appears to be limited to between 3 to 7 MIDI Notes.
Typically though, the LinStrument is mapped to have a 12-tone-equal-tempered 4th (an interval of 5 MIDI Notes) or 5th (7 MIDI Notes) between each of the 8 rows, essentially enabling playing pitches between the rows in a manner similar to guitars or bowed stringed instruments.
Let’s examine the implications of the default row offset interval range in the context of some of the lower numbered equal divisions of harmonic 2 (ED2), aka, equal-temperaments.
Below is a helpful chart for visualizing how equal-temperaments 5 through 31 would be impacted by the default offset interval range of the LinnStrument.
In the leftmost column of the table is the number of the equal division of harmonic 2 (ED2); starting with 5 tone equal temperament, and terminating at 31 tone equal temperament.
Columns labeled MIDI Degree 4th and MIDI Degree 5th show the MIDI Note interval required to play the 4ths and fifths of the corresponding equal temperament. This is what musicians would use to determine the row offset interval for 4ths and 5ths in this small selection of equal temperaments on the LinnStrument.
The ED2 4th Cents and ED2 5th Cents columns conveniently show the sizes of the equal-tempered intervals in cents.
With this information we can see that the LinnStrument would accommodate 4ths between each row for equal temperaments ED2-07 (7 tone equal temperament) through ED2-18 (18 tone equal temperament), because the MIDI Note offset for these equal temperaments is within the range of 3 MIDI Notes and 7 MIDI Notes.
Similarly, the LinnStrument would accommodate 5ths between each row for equal temperaments ED2-05 (5 tone equal temperament) through ED2-12 (12 tone equal temperament), because the MIDI Note offsets are also within the range of 3 MIDI Notes and 7 MIDI Notes.
So, as we can see, due to the default range limitation of possible offset intervals between each row – again 3 to 7 max MIDI Notes – the LinnStrument would only accommodate 4ths and 5ths between the key-rows for a very narrow range of these lower numbered equal temperaments.
In other words, where the musical goal and context requires mapping a complete equal-temperament to the controller, any equal temperament with 4ths greater than ED2-18 and 5ths greater than ED2-12, would not be possible with the factory default row-interval offsets, which immediately excludes intonation choices such as the historical favorite ED2-19 and the currently popular ED2-22.
With intonation systems outside of these 4th and 5th offset ranges, xen-micro musicians and composers working with the defaults of the LinnStrument would only have this limited offset range available between the key-rows, which could potentially constrain the full expressive performance possibilities with these microtunings.
Considering the larger implications for performing and composing in a nice swath of equal temperaments, it would be ideal if this range could be set arbitrarily to at least a range of 2 MIDI notes, and up to a maximum of 24. Being able to set it to a max row-offset interval of 24 MIDI Notes would accommodate the near-just 5th of ED2-41 (41 tone equal temperament) at 702.439 cents.
Another important consideration here as well, is that the MIDI standard only permits 128 notes on a MIDI Channel, so extremely wide row offset intervals might easily exceed this when playing across the range of the LinnStrument, requiring transposition of the individual rows to keep them within a musically useful and playable range. Obviously there would be context dependent performance gains and compromises according to the intonation systems in practical use.
Of course, it should be easily apparent that one could take subsets (such as MOS and so forth) of larger microtunings and these could be mapped to varying degrees of success on the LinnStrument, but larger offsets would be required where musicians and composers might want to have a complete large equal-temperament (> ED2-12) mapped to their virtual instruments.
It does appear from the documentation on the Roger Linn Design web though that this offset interval could potentially be expanded by writing some custom firmware code for the LinnStrument. This is my hope anyway, as my personal musical requirements would need a range greater than the default of 3 to 7 MIDI notes.
If you are a xenharmonic or microtonal musician who already owns a LinnStrument, and are actively using it in your music, please feel free to share your experiences, perceptions and insights in the comments of this article about how you are dealing with these matters. It would be good to hear from you.