Hello Guys, 
this is my first Post in this Forum, but I follow this Forum and using M-PC / Onyx for Years. I have done couple of Live Shows and Tours as a Light Operator and Light Designer in Germany and EU. The Bands I toured with use all the Symatics Audio Player for Playbacks/ Clicktracks / Midi.
In my Touring workflow I pre Program the whole Show at Home.
If I use Onyx for the Lightshow, the AudioPlayer send me a Midi Note to trigger the next Cue of the Song. Every Song has its own Cue List in a separate Playback Button. Every Song has its own Midi Note to trigger the corresponding Playback Button. (If I’m on a MA2 System I’m using LTC Timecode to trigger my Sequences and controling my Faders.) But with ONYX I use a Raspberry Pi to translate Midi to OSC and send the OSC Massages via Ethernet from Stage to my FOH Light PC to control Cue Lists and Faders.
But back to the Topic:
So the BPM in every Song is fixed. And in the past it cost me 10 to 15 minutes of stupid adjusting the FX SPEED to the correct Value to store the Speed in a Preset. To Save time i start a bit of research and calculations with Excel. The Speed Value is not linear to the BPMs its like an exponential function.
After some hours i found the Magic Formula to calculate the right SPEED Value for BPM.
FX Speed = square root of ( BPM * 3276,8)
for excel: =SQRT(80*3276,8)
some examples:
BPM 80 = 512 (Onyx say 500 but this is not correct its 512 
)
BPM 75 = 496
BPM 105 = 587
BPM 130 = 653
I’m still using Version 4.2.1057.0 and it’s only tested on this Version, but works nice for me, and I think it’s the same on newer Releases.
I love to share the formula with you to save your time if you use this type of workflow. And I hope that the FX SPEED System will be fixed in the future to a BPM System to synchronize easy the Lights to the Music.
Stay healthy
Greetings from Germany
Labbi