soittimiensa
Soittimiensa is a Finnish word that translates to "their instruments" or "of their instruments" in English. It is a possessive form of the noun "soitin," which means instrument. The suffix "-nsa" indicates possession by a third person plural subject, meaning "their." For example, "Heillä on soittimiensa kanssa harjoiteltavaa" translates to "They have practice to do with their instruments."
This grammatical structure is common in Finnish, where possessive suffixes are attached directly to the noun