How many of sang כי אשירה שבת to the tune of the Anthem of Sisvatopol - an Ottoman military song?
A lot of sephardic music is Hebrew words with appropriate themes set to music taken from the nations where we are in golus. Rav Ovadia says in Yechave Da’at vol 2 teshuva 5 that the general principle in Sephardic music is על ערבים בתוכה תלינו כנרותינו. In fact, many sephardic songbooks tell you the name of the Arabic song that the song is set to. So I don’t find this particularly surprising.
But it is nice to learn the origin of this particular melody. Thanks for finding it.
And a lot of Chassidish tunes are also borrowed. Keil Adon in particular has been done to a lot of 19th century Waltzes.
And Mod-O shelichei tzibbur often use secular music, from around the Gen-X era. Old and well-known enough that most of the shul can sing along.
Yashar Reggio argued that the mizmorei tehillim that start with אל תשחת עמך are referring to the niggun that we read the passuk of אל תשחת עמך in Devarim 9:26. See R. Eliyahu Benamozegh (Eim le-Mikra to Deut. 9:26) who discusses this.
Kol Tuv,
Reuven Chaim Klein
Beitar Illit, Israel