An input device for operating a digital musical instrument having musical behavior of string instruments, comprising: a) a key plate unit containing a set of input keys to be pressed by a player, in order to generate a first set of electric input signals, which emulate a combination of pressed keys of a musical instrument or a combination of pressed strings; b) a stick unit with variable tension of displacement comprising: b.1) a stick to be moved by said player between predetermined discrete positions, which emulate a combination of strummed strings of a musical instrument, said stick consisting of a replaceable modular handle that rotates a pivotal rod around a fixed pivot, responsive to movement and force applied by said player; b.2) a set of electric contacts, each corresponding to a different discrete position, for transmitting stick position signals; b.3) a string board with several spaced semi-tubular grooves, each formed in a different angle, which corresponds to a discrete possible position of said stick; and b.4) a stopper that restricts the movement of said pivotal rod in a discrete position when aligned with one of said semi-tubular grooves; c) a processing unit comprising: c.1) input buttons for setting musical parameters; c.2) a first set of interface inputs for receiving said stick position signals; c.3) a second set of interface inputs for receiving said first set of electric input signals; c.4) a memory for storing processing software; c.5) at least one processor, connected to said memory, for jointly processing said stick position signals and said first set of electric input signals using said processing software, and for outputting electric output signals representing codes of musical notes that correspond to movements of said input keys between pressed and released positions, and movements of said stick between said discrete positions; and d) one or more interface connections, for transmitting said electric output signals representing codes of musical notes, from said processing unit to a computerized tone generating unit that converts said electric output signals to sounds. a) a key plate unit containing a set of input keys to be pressed by a player, in order to generate a first set of electric input signals, which emulate a combination of pressed keys of a musical instrument or a combination of pressed strings; b) a stick unit with variable tension of displacement comprising: b.1) a stick to be moved by said player between predetermined discrete positions, which emulate a combination of strummed strings of a musical instrument, said stick consisting of a replaceable modular handle that rotates a pivotal rod around a fixed pivot, responsive to movement and force applied by said player; b.2) a set of electric contacts, each corresponding to a different discrete position, for transmitting stick position signals; b.3) a string board with several spaced semi-tubular grooves, each formed in a different angle, which corresponds to a discrete possible position of said stick; and b.4) a stopper that restricts the movement of said pivotal rod in a discrete position when aligned with one of said semi-tubular grooves; b.1) a stick to be moved by said player between predetermined discrete positions, which emulate a combination of strummed strings of a musical instrument, said stick consisting of a replaceable modular handle that rotates a pivotal rod around a fixed pivot, responsive to movement and force applied by said player; b.2) a set of electric contacts, each corresponding to a different discrete position, for transmitting stick position signals; b.3) a string board with several spaced semi-tubular grooves, each formed in a different angle, which corresponds to a discrete possible position of said stick; and b.4) a stopper that restricts the movement of said pivotal rod in a discrete position when aligned with one of said semi-tubular grooves; c) a processing unit comprising: c.1) input buttons for setting musical parameters; c.2) a first set of interface inputs for receiving said stick position signals; c.3) a second set of interface inputs for receiving said first set of electric input signals; c.4) a memory for storing processing software; c.5) at least one processor, connected to said memory, for jointly processing said stick position signals and said first set of electric input signals using said processing software, and for outputting electric output signals representing codes of musical notes that correspond to movements of said input keys between pressed and released positions, and movements of said stick between said discrete positions; and c.1) input buttons for setting musical parameters; c.2) a first set of interface inputs for receiving said stick position signals; c.3) a second set of interface inputs for receiving said first set of electric input signals; c.4) a memory for storing processing software; c.5) at least one processor, connected to said memory, for jointly processing said stick position signals and said first set of electric input signals using said processing software, and for outputting electric output signals representing codes of musical notes that correspond to movements of said input keys between pressed and released positions, and movements of said stick between said discrete positions; and d) one or more interface connections, for transmitting said electric output signals representing codes of musical notes, from said processing unit to a computerized tone generating unit that converts said electric output signals to sounds.