Translation:The Greek musicians are playing music, and the famous Polish singers are singing.
És is the pure "and", so to say. A conjunction that's connecting words and phrases.
Pedig and meg are postpositions and might be better translated as "whereas" or "however". They denote a contrast between two phrases. Like here, where the musicians play music whereas the singers are singing.
The meg in this sentence doesn't belong to énekel, it's not part of the verb. Rather, it is a postposition to a híres lengyel énekesnők and translates in English to "and", "whereas".
Dictionaries suggest "együtt énekel" (sing together) or kísér (accompany) for "to sing along".