When was the last time when serious new instrument was invented ?


I don't see anything new. Did I miss something ?

inna

To answer the OP's question,  if you discount synthesizers and other electronic devices, I would have to say it was the saxophone, invented by the Belgian instrument maker Adolphe Sax in the early 1840s and was patented on 28 June 1846. A very serious instrument.  

Pedal steel guitar, synths, electric piano, clavinet and Hammond/Leslie organ.