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 first played in German-speaking regions, and then spread 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 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.
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 favorably reviewed, but nevertheless it soon became popular. It had also become popular with New Yorkers by the mid-1840s at the latest.