Try this. Play a piano part into the sequencer (no drums). Quantize it, make it tight. Now play ANOTHER piano part with it, but make it quieter than the track you are recording... Hard, isn't it? If you can't distinguish what YOU are playing and what is the track, it makes keeping time much harder.

It's REALLY hard to play drums to a drum track turned down, because you immediately swamp out what you are listening to. There's a reason they use click tracks for recording... it is because the sound is different to anything the drummer is playing.

Essentially, you need a separate output on your arranger from whatever the track is coming out of. I don't know if the Tyros HAS a separate click out, but if it has, you route that to the drummer's monitor, along with the track. Preferably, he has in ear monitors or headphones (you would be surprised at how loud he will need the click, if he is using speaker monitors, it will probably be loud enough that the audience would hear the click - not good!).

If the Tyros doers not have a click out, you will have to create a separate track on all the SMF's with a click sound every quarter note (crotchet), and route that to the auxiliary outs, and route THAT to the drummer's headphones.

Oh, and don't worry about creating a tempo track that 'moves' a bit. Either he can play to steady time or he can't. If he can't... his drift will be different every night so creating a track to match him will be an exercise in futility. Just keep the tempos exactly where yuou are already used to them. If he can't play with them, get another drummer!
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An arranger is just a tool. What matters is what you build with it..!