I have an instrument called a Huaca that is a three chambered clay vessel flute. So as a wind instrument it plays three note chords. I have always thought of it as a fixed pitch instrument as it is not designed to play in multiple keys. It is mostly great in one key and can adapt to another by focusing the playing of certain notes but basically one key. Whearas the piano can play in all the keys so I have not thought of it as a fixed pitch instrument (even though the notes are fixed). I now see that it is considered a fixed pitch instrument. What would I call my huaca if not a fixed pitch instrument? What complicates it is that I can bend tones by shading the finger over the hole. Lastly I have tuned them to just intonation or what I call proportional harmony. Essentially how do you all differentiate between a fixed pitch instrument and a non fixed pitch (fretless strings?) and help me understand the nuances. Thanks.
Sounds, maybe, like the old harpsichords' just tuning, where pieces sounded great in just one key. When it was realised that 12tet tuning , although a compromise, could work in all 12 keys that sort of superceded other systems. Also sounds like your huaca is fixed and can't be changed, so will sound better in only one key. The fact that you can 'bend' notes seems like a way out. Interesting!– TimDec 4, 2016 at 18:53
1Could diatonic be the word you're looking for?– Todd WilcoxDec 4, 2016 at 19:19
2As far as I know, "fixed pitch" has nothing to do with temperament or possible keys, but solely means that the instrument has a certain number of discrete and unchanging pitches available, with nothing in between- such as, say, a piano as opposed to a violin. But of course the line is not hard and fast- fretted instruments have pitches "fixed" by the frets, but the notes can be bent, for instance.– Scott WallaceDec 4, 2016 at 20:14
If you can put up with the inane rants embedded in this article, there's a useful discussion of fixed-pitch vs. variable-pitch instruments and how they might work or not work together kurticus.com/fixed-pitch-and-adjustable-pitch-instruments– Carl WitthoftDec 5, 2016 at 13:44
Interesting. Clearly there are fixed pitch instruments, such as one-piece flutes and whistles, or tubular bells or whatever. Then there are variable pitch instruments such as the violin family. And there seems to be a third group: tuneable but bloody awkward - anyone ever tuned a church organ?– JimMMar 9, 2017 at 14:38
A fixed pitch instrument is one that cannot be tuned. It has nothing to do with whether you can play in more or fewer keys. For instance, I play the pennywhistle. My whistle is a single piece of aluminum tubing, and can not be tuned. It is a fixed pitch instrument. But I could spend more money and buy a pennywhistle with a tuning slide. With either instrument, it only playes comfortably in a couple of keys, but with a tuning slide, I could tune to A = 440 hz, or A = 430 hz.
A piano can be tuned, but it needs an expert, specific tools, and a fair amount of time. So while you could argue that it's less fixed pitch than your clay flute, for practical purposes it's fixed because if you sit down at a piano, you can not tune the instrument so that the keys are at a different pitch.
A guitar, violin, or concert flute (for example) can be tuned by the musician in under a minute, and will be tuned before each performance. These are not fixed pitch instruments. If they play with a fixed pitch instrument, everyone will tune to that instrument.