Notblind, would you please provide documentation for this? I'm not doubting but I'd really love to have the source so that I can share it with others.
Sure:
Proclaimers book page 241:
Although singing in local congregations was largely dispensed with in about 1938, it was revived again in 1944 and continues to be a significant feature of the congregation meetings and convention programs of Jehovah's Witnesses.