The One most interesting is (for me) the Synth DX 747.
A Fm synthesizer based on the DX7 and that can exchange presets with the original hardware.
There has only been one more advanced Fm synthesizer on Android before this (to my awareness) being called SynprezFM but it does not have midi implemented.
Got this last week and it sounds good but have still not connected it to a midi keyboard but it promises low latency by using proprietary methods. Which luckily is a problem going away in either case when it comes to newer devices and the latest Android updates!
Specially when it comes to midi as the interface is not interfering with the latency.
I like the idea to have proper FM synthesizer available that is midi controllable, and being digital have a hard time believing that it will sound different from the original using the same set-up and the DX7 being digital in the first place.
So anyone looking for shimmering pads and bell like tones here is your answer!
Plus a reverb/ delay built in.
It goes for 3.99€ but there is a free version with around fifteen presets that are totally workable for free and as the bigger version with the low latency.
So if there is a lack of a groovebox it can be worth checking out as it costs about as much as air.
It can do synthesizer sounds and drums using a sequencer grid as is pretty common fare on many apps.
Here is the links from top to bottom: