Over the next several decades, various improvements were made to the accordion. One major modification was made in 1850, when the chromatic accordion was introduced. The early diatonic accordions produced different notes when the bellowswere drawn opened and pressed closed. The chromatic versions produce the same note regardless of the action of the bellows. Steel reeds were incorporated into the instrument in 1857. The addition of more bass keys was particularly important.
By the early twentieth century, manufacturers had settled on a standard size and shape for the instruments, which eventually led to the modern accordion, some of which are digital and will emulate the sound of a full orchestra.