Wikipedia

The accordion is a free reed instrument and is in the same family as other instruments such as the sheng and khaen. The sheng and khaen are both much older than the accordion and this type of reeds did inspire the kind of free reeds in use in the accordion as we know it today.

8-key bisonoric diatonic accordion (c. 1830s).

The accordion’s basic form is believed to have been invented in Berlin in 1822 by Christian Friedrich Ludwig Buschmann, [notes 4] although one instrument has been recently discovered that appears to have been built earlier.

Zitat Dillner Akkordeon

The accordion is one of several European inventions of the early 19th century that used free reeds driven by 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 Instrument with piano keys had been invented in 1821, but it started to actually be played much later, and built it’s 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. [notes 7]

By 1831 at least the accordion had appeared in Britain. The instrument was noted in The Times of that year as one new to British audiences and not favourably reviewed, but nevertheless it soon became popular. It had also become popular with New Yorkers by at least the mid-1840s.

The musician Adolph Müller described a great variety of instruments in his 1833 book, Schule für Accordion. At the time, Vienna and London had a close musical relationship, with musicians often performing in both cities in the same year, so it is possible that Sir Charles Wheatstone (inventor of the concertina) was aware of this type of instrument and may have used them to put his key-arrangement ideas into practice.

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 are operated with the left. When the two instruments are combined, the result is quite similar to diatonic button accordions still manufactured today.