On good resource I have found is in old libraries, especially in smaller rural towns. I often find old records which have amazing recordings of the famous and not famous, & sometimes songs I have never heard before.

Maire-aine, I have heard many old recordings in which the lady singing was also playing the Piano. I have heard several ladies who were blues singers telling of how they played Piano or Organ for Church-& most of them sang in the choir. Sometimes one may find an old Hollywood film which has scenes where a well known singer plays piano as they sing. It stands to reason that they also played other instruments.