The present invention provides in combination, an intonated string nut and string-locking mechanism for a musical string instrument with a fingerboard where the combination intonated string nut and string-locking mechanism includes a string-nut fulcrum and a string-locking means, where each string-nut fulcrum may have a varying linear position in relation to each individual string in order to provide the optimum compensation amount for improving the consistency and production of in-tune musical notes during play for musical string instruments with fingerboards. Also disclosed are methods of use of various embodiments for the intonated string nut and string-locking mechanism.