Yamaha Electone EL-57 Owner's Manual page 91

3) AWM Operators
Each algorithm also has a special AWM (Advanced Wave Memory)
Operator. AWM Operators are not sine waves like the other Operators,
but are digital recordings of actual instrument sounds, such as piano,
violin, guitar, and so on. The AWM Operator's sound is mixed with the
sounds of the other Operators in the algorithm to create realistic voices.
You can adjust its output level within the range: 0 - 127.
AWM Operator
7
87