Depends on how you define "a whole song", but I'd say theres plenty of other options. In fact I'd go so far as to say the polyend tracker is even better than the op-1 for that purpose. Even better than that, a standard laptop with a standard DAW. Or even an ipad for that matter, which has a great selection of its own software.

There are many things the OP-1 does that nothing else can do quite the same, but I wouldnt say thats one of them.