A friend of mine told me that there is a problem with listening to a cappela during sefira. A few people mentioned a few places where it talks about it but I don't remember the places. What is the source for this?
Matzav has a Psak from Rabbi Yisroel Belsky differentiating if it is a choir or a Capella. A choir (without music) is permitted and a Capella which sounds like music would be prohibited.