This is the 1160th most frequent Polish word.
ulicach
"Ulicach" means "streets" (locative plural form) in English.
Here, 'ulicach' is in the locative plural form referring to 'streets' as locations where the action occurs.
Na ulicach miasta pojawiły się barwne dekoracje.
Colorful decorations appeared on the city streets.
In this sentence, 'ulicach' again is in the locative plural form, indicating the place or surface where walking occurred, specific to 'streets'.
Spacerowaliśmy po ulicach starego miasta.
We walked through the streets of the old town.
In this context, 'ulicach' conveys the idea of streets as locations where something (sounds of music) is present or happening.