Any tape used in the production of a master tape. For example, if a master tape is an equalized (or otherwise processed) copy of an earlier tape, the earlier tape is called the sub-master.
"I was visiting my mother this last weekend. Mom is 90 and hasn't heard her brother's voice for years. My brother and sister had never heard Uncle Bob. I took the opportunity to play the CD. All of them commented that they were surprised that I could get the records transferred to a CD. In addition, the clarity was very good. I expected to hear ..."
