In the case of the R-44 you can use the pre-record facility* to give you an almost-seamless split at a point of your choice - as I recall it, something like 100th of a second is lost - which sounds like the 661 "autotrack" facility. So you pick a spot like applause and do your manual split there, where it won't show. Wouldn't that be sufficient in almost all real-world situations?
[*What you do is have prerecord on, press 'stop', press 'record', and the pre-record buffer takes over in the gap between you pressing stop and record, dumping the buffer onto the card at the point you press 'record'.]