Mellotrons are largely obsolete but are still being made in small quantities. Today, digital instruments have mostly taken their place. Digital keyboards are portable, and can be used to make similar sounds anywhere. While digital keyboards have been used since the 1980's to replicate the sounds of many other instruments, they cannot accurately replicate the nuances and idiosyncrasies of the Mellotron because of complex physics involved in the tape playback system. This acknowledged drawback has led to the production of new Mellotrons since 1999. 