There are two versions of SK880:

1) Sk880

2) Sk880ps: It has a harddrive.

Sk880ps:

a) 2meg backed memory: 8megs optional (but I strongly believe it is a must)
b) vocal harmonizer: optional
c) 88 keys weighted hammer action
e) no speakers
f) harddrive

Wk8:
1) 61 unweighted keys
2) 8megs backed memory
3) vocal harmonizer
4) harddrive
5) speakers

Q: would it copy for the whole song or just a measure?

It is absolute beauty:
It can copy the whole duration of a song, or a measure or a range of measures. It can do this for all tracks or a particular track. Your control is unlimited.