Ahhhhh, so it works!!
Thanks Alto, that's a great relief.
I agree it's not perfect, but the MIDI trigger feature is the only way to get the 4K to sample audio in sync with the song, meaning that when you insert that MIDI note later on to trigger the recorded sample, you exactly know where to put it in the track, because you told the machine exactly where it should start sampling (mostly in the beginning of the track).
My RS7000 (also a sampler/sequecer) goes a little farther: it supports a record mode where you start recording a track, and nothing happens until audio starts coming in. The RS actually remembers *where* in the track that was, and after the sampling is stopped it automagically inserts a MIDI note on that track at that remembered position to trigger the new sample. So even if you start playing somewhere in the middle of the track, the RS will insert that note at exactly that spot in the track. Saves a lot of wave memory!
Something like this would be great for the 4K.