After some trial and error I found that the E463 keyboard can only transmit on channel 1, however in song mode the keyboard receives data on any midi channel 1-16 (only 1-5 for the melody).
So that the external midi device must be setup to receive data always on channel 1 for the recording phase, while the transmit channels must then be different for each track so that 1-5. At that point the E463 will playback the midi song from the external device using the voices selected for tracks 1-5 in its internal recorder (always song mode).
Clearly, the biggest advantage of using an external midi recorder is much higher editing capabilities vs. the E463 recorder, i.e. quantize, cut/copy/paste/insert/delete beats, punch-in and overdubs, repetition of patterns, loops etc…
It’s obviously possible to export the full song all at once from the E463 in .SMF format at the end of the recording but personally I prefer to record and edit each single track on an external midi device one by one directly after any recording. So that i.e. by playing only a 4-beat arpeggio on the E463, I then can have a perfectly quantized background repeated for maybe all the lenght of the song on which I can try to build something else…
I’m using an iPad (not PC) and I find myself very well with SAND app, cheap and very simple to use, it is great with step and pattern composition.
The good of pairing the keyboard with an iPad (or any other tablet) is that is like working directly on a much bigger and more comfortable keyboard display in real time.
I hope this can help those who are interested!
