Does Tehillim 92 validate our ability or the specific mitsvah on Shabbat to sing praises “with speech upon a harp”? | If it’s already tuned what’s the error (to not fix a string if it breaks)? In the rare case one of those ten or fifteen strings breaks - Why not keep playing on the strings that remain tuned & unbroken (in honor of HaShem and the memory of this specific song)?
Taking into account that this was the Shir Shel Yom of Shabbat, the gemara in Sukkah 51a states:
"However, with regard to the song that the Levites sang accompanying an offering, everyone agrees that it [the playing of musical instruments] is part of the Temple service, and overrides Shabbat."
So in the most practical sense of the Psalm, i.e., when it is seen as referring to the singing of the Levites, it seems to perhaps have validated their ability to play instruments on Shabbat - during the Temple Service.