Is the accordian an experimental instrument?

The accordian probably would not be considered an experimental instrument although it is of more recent origin than many other instruments.

The accordion is a free reed instrument. The accordion's basic form is believed to have been invented in Berlin in 1822 by Christian Friedrich Ludwig Buschmann, although one instrument has been recently discovered that appears to have been built earlier. The accordion is one of several European inventions of the early 19th century that used free reeds driven by a bellows. An instrument called accordion was first patented in 1829 by Cyrill Demian, of Armenian descent, in Vienna. Demian's instrument bore little resemblance to modern instruments. It only had a left hand buttonboard, with the right hand simply operating the bellows. One key feature for which Demian sought the patent was the sounding of an entire chord by depressing one key. His instrument also could sound two different chords with the same key; one for each bellows direction (a bisonoric action). The piano accordion was played in German speaking regions, then all over Europe. Some early portable instruments with piano keys had been invented in 1821, but it started to actually be played much later, and built its reputation from there. At that time in Vienna, mouth harmonicas with Kanzellen (chambers) had already been available for many years, along with bigger instruments driven by hand bellows. The diatonic key arrangement was also already in use on mouth-blown instruments. Demian's patent thus covered an accompanying instrument: an accordion played with the left hand, opposite to the way that contemporary chromatic hand harmonicas were played, small and light enough for travelers to take with them and used to accompany singing. The patent also described instruments with both bass and treble sections, although Demian preferred the bass-only instrument owing to its cost and weight advantages. Jeune's flutina resembles Wheatstone's concertina in internal construction and tone color, but it appears to complement Demian's accordion functionally. The flutina is a one-sided bisonoric melody-only instrument whose keys are operated with the right hand while the bellows is operated with the left. When the two instruments are combined, the result is quite similar to diatonic button accordions still manufactured today. Further innovations followed and continue to the present. Various buttonboard and keyboard systems have been developed, as well as voicings (the combination of multiple tones at different octaves), with mechanisms to switch between different voices during performance, and different methods of internal construction to improve tone, stability and durability.