There isn't one specific thing about Mugician that makes it special or unique. But what does work well is a combination of things:
- Keep latency low at all costs. An instrument with perceptible latency is most likely useless to a skilled musician.
- Go fretless, and put up with the initial learning curve that it imposes. If I cave in to requests to make it snap (ie: autotune) to notes, then I am suddenly back to something that sounds too electronic. At that point, everybody want's a post-processor to "humanize" the tone. It also takes away what is superior to this layout: microtonal things that are readily available to singers and violinists - in a keyboard-ish layout.
- Make the spots for a finger about the size of a finger, so that you can play fast. This makes two-handed finger-tapping technique work really well.
- Use the time-honored guitar (fourths) layout, rather than the piano layout. There is precedent for this inside and outside the app store, btw.
- Make the instrument as stateless as possible. You don't want to be going crazy in a solo and have everything blank out on you with a window that you need to close.
- A practical, flexible sound. If you are a working musician, especially a metal musician, then flexible distortion and reverb are going to be the cornerstone of your sound. I didn't go the route of sin/saw/tri/square waves. That is stuff that is done mainly because it was easy in hardware; not so much because it sounded better than overdriven tube amps. I didn't go the route of samples either, because they end up being too specific; leading you to needing a gui with a librarary of discrete samples to choose from, and no continuous blending of them.
- All change is continuous, from voicing to expression and fretlessness.
This is a video that I quickly hacked up in order to show the latest version of Mugician to a reviewer. I am kind of out of practice as a musician. I presume there are a lot of people that can do better than my demo playing. But here is a clip:
You will notice in the video that usually when I put a finger down, the note turns Green. That color is used for when you play "in-tune" with the nearest semi-tone. When you see red dots, that is when it is "out-of-tune" with the nearest semi-tones. These are not necessarily mistakes, but important tones to have.
When sound is viewed in terms of physics, the black and white keys are actually out of tune by any reasonable definition of what the tones should be. Vibrating bodies have overtones that are integer ratios to the fundamental tone. Most microtonal systems adjust the fourths and fifths to be perfect, so they don't match piano. Just intonation tries to place notes such that there are small integer ratios - an effect similar to what you hear when playing around with analog electronics. They can be somewhat close to the standard tones, but they can't exactly match because the 12 tone system is a completely artificial approximation of the physics behind the sound.
Microtonal music, which was typically formulated before the 12 tone system, therefore usually features such tones. Middle Eastern music is the most obvious place to find practical uses for quartertones, where notes are in between what would normally be the black and white keys. In a lot of ways, heavy metal is a bad imitation of these scales, crippled by the fact that they are playing guitars with frets on them.
This isn't the only example of microtonal music, but to be sure, this is where you should start if you want to learn how it usually arises in practice. It mostly boils down to when you play a minor scale, you stretch the third and sixth interval to be ambiguous between major and minor. The core pentatonic scale is still there; but now there is a note exactly half-way in between its wide intervals. When you play in a style with a lot of accidentals, using these in the right places gives you options you never have on any fretted instrument.
My hope for Mugician is to help break open new music genres, and take fretless metal ensembles into the mainstream. The more an instrument does for you, the less you can hope to become really good at it. If you can't play out of tune, then that's one dimension of your personality that disappears; ditto for fixing your rhythm. By the time the computer fixes everything, you can't tell who is who by ear alone.