I’ve been trying to sync Hydrasynth Explorer tempo with BeatBuddy? Is it possible? How?
What have you tried?
And which one is the master? Hydrasynth? So you take midi out from Hydrasynth and feed it midi in to BB, right?
I’d guess that should work if Hydrasynth sends tempo messages 
This you might have to use some monitoring tool to be sure 
Another question is your workflow. If you set the tempo after selecting a beat then all is good. If the other way around you need to select from settings that BB doesn’t change tempo when changing beat 
Haven’t tried yet, as I just noticed the BB midi port is smaller than my midi cable connectors.
I want to control the tempo of the synth with the BB because I haven’t found a tempo knob on the synth (ASM Hydrasynth Explorer), only a “tap tempo” function.
I like the ability to dial in the exact tempo on the BB. So am assuming midi cable from BB to synth midi in port will work for that.
However there is so much I don’t know, and my assumptions thinking have led me astray in technical matters.
Will the BB breakaway cable work, or are there more technical considerations to take into account?
I use the BB in/out cable (I guess it’s called breakout) that Singular Sound sells, but in addition you need another male-male 5-pin midi cable (but I think you have one already) 
And just keep exploring, that’s the best way to learn