Sefer Eshkol (vol 3, pg 129), Maharikash 217, Nishmat Adam 4:11, Kaf HaChaim 75:27 holds that it’s a rabbinic prohibition, however, Tzel Kesef (vol 2, Maarechet [[Brachot]] 40:5) holds it’s a biblical prohibition. Sdei Chemed (Kuf, Klal 42) quotes other achronim who argue about this.
*In conclusion, there’s a major dispute whether this is a biblical or rabbinic prohibition. Sh”t Yabia Omer 1:6(10) writes that it may be considered a rabbinic prohibition when taking into account other considerations. Mishna Brurah 75:17 quotes the Chaye Adam (same author as Nishmat Adam) and seems to agree with those who say it's a rabbinic prohibition.</ref> Therefore, one is not allowed to listen to a woman singing. <ref>Shulchan Aruch O.C. 75:3, Shulchan Aruch E.H. 21:1 </ref>
#This prohibition applies at all times and not just when one is reading Shema. <ref>Shulchan Aruch E.H. 21:2 </ref>
==Who is Included?==