Yamaha Electone EL-900m Owner's Manual page 44

Different disks in the disk copy operation.
(Ex: 2HD disk is inserted as the copy destination while 2DD disk data has
been read as the source.)
(Ex: 2DD disk is inserted as the copy destination while 2HD disk data has
been read as the source.)
Answer: You have to prepare the same disk type as that of source disk.
Reading error.
The destination disk has not been formatted.
Answer: Press the Data Control buttons under [Format] to execute
formatting operation, first.
You can also change disk and insert a formatted disk.
Others
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