An instrument is a concrete or abstract tool intended for a purpose other than mechanical work, in particular a refined one.
Musical instruments are devices designed to produce music, frequently by plucking or striking a string or bell or drum surface, or by forcing air to resonate (see wind instruments).
... (in/at/by them) at the end of the second line is in locative
plural. Translated: "...in them".
History
Sanskrit is the oldest member of Indo-Aryan[?] sub-branch of ...