I found the post where Georges Frederick Litterst says that the Mac finder from 10.7 cannot see the dkc and its suggestion to use mucommander:
"George Frederick Litterst
Aug 22, 2013
Good morning, everyone.
I have learned officially that the E3/DKC-850 cannot be accessed by the Mac Finder in OS X 10.7 and OS X 10.8. However, there is a free program called muCommander (http://www.mucommander.com) that will provide access to the From/To PC folder.
The program presents a window with a split screen. On one side, you access the directory of your Mac. On the other side, you access the E3/DKC-850. To access the E3/DKC-850, you must specify SMB as the protocol and put in an address similar to this:
To find the "dkv" number for your Disklavier, you can do either of two things:
(1) Note what dkv number shows up in the sidebar of a Finder window in the "SHARED" section.
or
(2) On your Disklavier, go to Setup : Network : Information : Name
When you use muCommander to log into your Disklavier, a window will pop up asking for a username and password. You can log in as a guest without a username and password.
NOTE: muCommander will only give you access to the From/To PC folder. If you want more functionality than that, you should get DKVBrowser (http://dkvbrowser.sourceforge.net). To use DKVBrowser, you'll need to identify the current IP address for your E3/DKC-850. To do so, go to Setup : Network : Information : IPAddr.
Regards,
PianoBench"
Now there maybe other workaround... I will eventually try to find a wifi bridge to test the wireless connection.