DIATONIC VS. CHROMATIC VS. PRIZIM SETUPS
Each has it's advantages and disadvantages...a trade off of things...like comparing a LeMans racer with a Jeep. But for me, the whole debate hinges on the issue of borrowed chords. A borrowed chord is a chord that doesn't exist amongst your diatonic chords...most common the V7 of V (what we call, in folk, the II7)....like D7 in the key of C. Another common one would be the flatted VII chord...a Bb in the key of C. These are both borrowed from keys on either side of our chosen key...hence they are called neighboring keys...There are lots of others, too, many borrowed from non-neighbor keys...like the E7 that pops up in the key of C...it's the V7 of the relative Amin chord, but we find it down in the key of A (unless we are playing a 15 chord chromatic!). In "theorese" it's called the picardy third.
Diatonic has a fine full sound....but to get this sound, we must simplify/limit the music we play. It's a little like taking the passenger seats out of a car to make it a better racing vehicle (the LeMans racer).... yes, it performs better on the racetrack....perhaps in competition....but not on a family vacation or camping trip. But what if I don't have the borrowed chord on my diatonic??
If I limit the scale of my harp to 3, 2, or 1 key(s), am I moving forward or backwards? Well, it depends....if I do it, I am gaining volume (but there are conditions to this) and richness. I also gain the ability to open chord, and this is a technique that every autoharpist should learn to do to advance their skill set. So in these regards, I'm moving forward...and it's a forward direction that I must go in to advance my harp skill set.
The fine full sound of diatonic is addictive to the point of exclusion...many many 'harpists, when they get an earful of that sound, will park it there on the diatonic harp for the rest of their days, thinking they've arrived. They feel they can play smoother and faster, and who doesn't want smooth and fast? So, granted, Diatonic AH has an accompanying skillset that is "must learn" stuff. But it's not the end-all. Much Diatonic playing can sound blurry, (the flip side of "choppy" chromatic playing) and the limited repertoire of the diatonic, can sound, well, limited, if not mixed in with music that branches into more chromatic tonalities. If we only play all-open chorded music, we are making ONE SOUND all the time. Whole musical eras and styles (indeed MOST musical eras and styles) must be passed over in order to accomodate the limited palette the Diatonic Autoharp provides.
In my opinion, Diatonic is not the best choice to accompany singing, for several practical reasons: It's not flexible enough to offer the singer a range of keys to select the best for their voice. You have to run with many harps. (You KNOW you have to load that LeMans Racer into a trailer to get it to the track....it won't even go in reverse!) It can easily be too loud, if one is not using amplification...and if we ARE using a vocal mic, then it's picking up the harp that's right next to your face, too! We are not typically trained vocalists, able to fill a concert hall with the power of our diaphragms. I have often listened to recordings of myself playing acoustically, and found that even my chromatic was louder than it should be, and I AM a trained vocalist. As "diatonicists" we end up schlepping not one, but sometimes four Autoharps....and if the music uses borrowed chords, what then?? Suppose we want to move down a step or two, but the harp that we happen to have for that key has the key at the wrong end of the harp, and borrows the chord from the wrong side...for example, what if we have an F/C harp...and want to sing in C, but the song has a D7, borrowed from key of G?? We're out of luck...again. In singing, isn't the focus supposed to be on the VOICE anyway? The harp becomes support...ACCOMPANIMENT, anyhow....and doesn't need to be a souped up racing vehicle. Luthiers will never tell you this....the more harps you need, the better! They are there to fulfill your hankering for that other/next harp that fills in the blanks of your key coverage.
Diatonic is a GREAT choice for SOME instrumental music--those tunes that HAPPEN to stay in the confines of the one key, or borrow ONE chord from the neighboring key to one side or the other, (two key diatonic in this case) and if you DON'T want to add notes to your chords. If you are playing solo, not singing and it doesn't matter if you are playing in G or F or what have you, then yes. And you may argue that you can fill up the chord bar array with extra chords so you can add other notes to the mix....but WHICH chords should you add to those--say--extra 5 bars you happen to have? Which ones should you leave out? So yes, for fiddle tunes and diatonic melodies, great.
So as for advancing by moving to diatonic....you pick up a few advantages...and you must learn open chording to advance as an AH player...highly recommended! But you also pick up lots disadvantages. Does a bird gain advantages by adding wings and dropping forepaws or hands? Certainly....and lots of limits too!
Then there's chromatic. It's got it's advantages and limits too. You can't play those smooth flowing cascades of open chording on a standard chromatic, and you don't have that rich diatonic double string sound. But you have the advantage of a broader repertory to choose from: add blues, add rock, add "the standards" from the past two centuries. Add classical. Even add 3 dim7 chords (there are only 3...with 8 names each) which are useful, not just for places where the songs call for dim7 chords, but for playing chromatic slides and walkdowns/ups. But speaking of limits, the chromatic is STILL limited to majors, minors and dominant7 chords (if you don't add the dim7s).
That's where the Prizim comes in. It allows you to add in those open chord advantages you put in from your diatonic playing...--not just in 1 2 or 3 keys, but FIVE. It allows you to add in maj7s, add9, min7, maj6, sus4, min6, and 9th chords...not just for a FEW of your chords, but for ALL of them, in all 5 keys. And the pattern is the same for all keys...shift over one button, and follow the same patterns...new key. The layout is basically the Bryan Bowers layout. I was playing melody within 15 minutes. Within a couple months, I was playing my whole repertoire of instrumentals on this instrument, it was very easy to learn/adapt. THe smooth open sound of the diatonic comes back, plus the ability to play even MORE repertoire...all those songs (well, most of them) that you couldn't play before, even on chromatic.... You even get back a lot of the volume you lost on the chromatic, because, even though it's one string per note, you have lots of chords where you are adding extra notes in....when you learn to do it....so you are playing four and five note chords instead of three note chords...more strings vibrating means more volume! On the Prizim, you can actually play up and down the whole major scale while never changing the chord: C D E F G A B.....all while keeping a C chord ringing....and you can do this with 7 different major chords. Another great advantage is that there are two ways/places to play minor chords and 3 or 4 ways of playing majors...which can simplify the fingering greatly in some passages...you are dealing with a tricky left hand pattern, and then discover that there's a much simpler way if you play the minor chords the other way.... Here's another Prizim advantage....to convert, you can just take a standard 21 bar chromatic and remove a few more notches of felt from each chord bar...and you are in business (3 must have their felts changed completely). The whole process takes at most an hour...(more of course if you want other keys than what you already have).
OK, but in the interests of full disclosure, what are the limits of the Prizim? What are the disadvantages? There are several, and most are easily overcome with some practice. Open chording on a Prizim is different than on a full diatonic..for one thing, you are holding down a button (a non lockable "lock bar") and opening and closing another bar to do it...for another (related) thing, the second scale degree is missing from that scale bar's scale....so to get "re", you have to quickly use another neighboring scale bar, or skip over the note. It's not as hard as it sounds once you get the hang of it....just another technique that you have to learn. Another is there are no standard 7th chords...but 9ths instead...which are 7ths with an added note in it. They sound MORE bluesy than a regular 7th, so not really a limitation. At first, I thought this would be a deal breaker...but it wasn't...I use the 9th in all the places I would use a 7th before, and now, to my ear, a regular 7th sounds hollow. Another thing is that it doesn't have that double string sound. But it makes up for that, as I said, by having the potential for adding notes (and thus more open strings) to any closed chord. Another limit is the fact that you are using two buttons at once much of the time. But just as often, only one. This is compensated for by layout...the buttons required for simple chords are laid out to "overlap" each other, or almost...so you can push them with one finger...making melody playing a matter of three fingers again (and the SAME three finger patterns you used before in most cases). Further, I suggest lightening up the springs and lowering the playing action as far as possible so the least amount of finger stress is exerted. As to volume, remember that I prefer chromatic to diatonic for songs....and I have played my particular chromatic next to MANY diatonics, and it's just as loud...it doesn't have the double string sound, but it's PLENTY loud....so that's a function of the particular instrument you are playing. Another "might be" disadvantage is the lack of precedent. There are not generations of accumulated wisdom as to how to move your left hand around the chord bars....you are sort of on your own to learn the array, and teach yourself how to use the buttons...and you will....finding your own ways of doing things and developing your own methods and making your own discoveries. There are no method books to teach Prizim playing...there wouldn't be many buyers, so who would publish such a thing? And the time it would take to write and format, for just a few interested parties would be prohibitive! I have played Prizim, exclusively, for 10 years now and I'm still discovering cool things I can do....and most of it was when I was allowing my hands to come up with "feats of daring do" that I had no idea existed. These reasons are why, for me, the Prizim setup is the ultimate combination of Diatonic/Chromatic, plus some. It solves many of the limitations of the diatonic, and adds in its advantages....it solves many of the limits of the chromatic, and adds in it's advantages. I can carry ONE harp and have the advantages of diatonic and chromatic with me. If I were concertizing, I'd have a diatonic with me too (It is great for those things it's great for!)...but since I'm busking, and really only want to carry one harp, for me, it's a no-brainer: a little bit LeMans, a little bit offroad.