Short story. I tried the formula device once. It crashed renoise. 
I never dared trying it again.
I think Jonas reported some of the bugs with it and some of them were fixed. Not sure if they got fixed for 2.7.2…
Anyway,
the formula device is still classed by the devs as ‘highly alpha and experimental’. so there is reasonable probability it will crash your Renoise. that means you should avoid using it in any worthwhile track for the moment.
for some real-life experiences with the device in actual attempts at making tracks, check out the DDRC 23: https://forum.renoise.com/t/dead-dog-renoise-competition-round-23/33843
hmm, went through this 2 page thread and i’m none the wiser.’
putting an A into the Formula portion, and binding the formula device to trackvolpan’s Vol, then moving A seems to control the volume.
but are BPM/LPB read-only, i.e. only accessible as numbers? Or could A be made to control BPM?
Cool… About a little bit of programming, I do see the User there and one could write to that… if one knew what to write.
So far it seems that the formula device does not directly have access to the transport ( LPB / BPM ), or if it does, it’s not dead-obvious (=obvious enough) to me.
This would be really swell for controlling an arpeggiator metadevice’s parameters tho.
sorry, meant ‘actual attempts at making tracks’, not ‘threads’. bit tired i suppose. editted the post.
what i meant was not so much that that thread shows you examples of formulas, but rather examples of experiences with usage of the device itself. in other words, it was an attempt to underline my comment on the alpha-ness of the device by providing you with a thread of people trying to use it in tracks and failing because of crashes etc.
i don’t have any real-life examples of formulas etc for the device because i suck at math and therefore have trouble making something proper with that device.
Don’t think so. All you can do is route the result of the formula to some other DSP chain device.
Maybe some interesting thing to do with it is complex automations over a longer time period, without writing down automation explicitely in the Automation tab.
You can create something of a kin to automation lanes or LFOs by entering formulas, with three controllable variables (A, B & C) a lot of built in functions and variables (pattern/song postistion etc) and more programmable via LUA.
So you could use it to create a simple automation that builds through an entire track with a few simple commands or use it to completely mash and modulate something by combing say a signal follower with trigonometric functions and much more.
Is there any possibility to directly address the audio stream with the math device, for example for programming a little synth?
maybe through a workaround using the dc offset device?
Hm, but what about also reading the audio stream, for example for processing it with some dsp math?
Is the formula device script based or compiled c++?
The formula device is a native C++ compiled device, so there is not much that can be tweaked outside the core dev-circle here.
Thanks for the info, I just asking because of theoretical performance of the formula device. So it would be theoretically possible to manipulate the audio stream with it… 
the formula device embed a stripped down lua interpreter so what you actually see there is plain lua. in fact in the user tab you can define your own lua functions and initializations, to be used in the formula itself.
i will soon collect some useful recipes i have here to explain its use cases.
mmm, recipes )
Also, this thread is a completely dead duck without this (thanks to kazakore from another thread ( Enabling The Formula Meta Device ) ):
[details=“Click to view contents”]<?xml version="1.0" encoding="UTF-8"?>
true
false
Init
false
true
Mixer
0.5
Device only
1.0
Device only
0.0
Device only
0.5
Device only
1.0
Device only
true
true
true
Init
true
true
A
B
C
true
1
0.0
Device only
0.0
Device only
0.0
Device only
-1
Device only
-1
Device only
-1
Device only
[/details]
Are you saying, that since I do know how to say
renoise.song().transport.bpm = 110
that the Formula part could be used to say, read A + LINE
and the User part could be used to do
renoise.song().transport.bpm = Formularesult
?
How would I go about doing that?
These would be appreciated very much!
Are you still not using Meta Devices a lot??
Basically you can create (amongst others) complexer LFOs, or LFOs that always have 4 cycles per pattern no matter how long the pattern, stuff like that. I used to make some chiptunes by typing in weird formulas, like sin(X+sin(X)) where X is something to do with LINEF/NUMLINES2PI - and then letting it control a DC offset and render the pattern. Voila a chiptune.
demo-formula.xrns
These kinds of waveforms are also what I mean by ‘complex LFOs’ - but usually, I’ll indeed just try using a couple LFOs with them bound to Offset or Amplitude or even Frequency of another LFO, throw some MMixers in etc.
tldr; I don’t really use it in a lot of songs, I did have a wobbly bassline with it once but I lost that xrns. It was fun to make, but because you can change only 3 params, I don’t know it’s still just a little bit made for the diehard…