"in the instrument" is correct and usable in written English.
You can use it when referring to a particular tool or device. For example, "The schematics for the engine are located in the instrument."
The locals set about unlocking voices hidden in the instrument.
She said she saw "huge opportunities" in the instrument market.
There are no Soller type collimators in the instrument.
Images were taken using a high-resolution camera implemented in the instrument system.
Depression is a malfunction in the instrument we use to determine reality.
Press it and all the dials in the instrument binnacle turn an angry red.
Few writers have approached his expertise in the instrument, its players and its literature.
From the 16th to the 19th century several changes occurred in the instrument.
No one will believe in the instrument they rely on for solutions.
The problem was that their families believed the spirit of the long-dead old masters still resided in the instrument.
That phase didn't last too long, and David Bowie played a major role in sparking renewed interest in the instrument.
