mØxr - CV Audio to MIDI Converter

Wednesday, June 15th, 2011 | 9:02 am and filed in Reason, Synthesizers.


mØxr is a MaxMSP based application that converts Control Voltages as audio signal to monophonic MIDI note messages. The application must receive two CV signals through audio connections, a Gate CV and a Note CV. While any audio signal can trigger a MIDI note message, mØxr is calibrated specifically for the Note CV values generated by a Thor Polysonic Synthesizer in Propellerhead Reason.

Discussions on the propellerhead user forum inspired me to pursue this idea, which began with the MOTU Volta concept of controlling analog hardware synthesizers with software based CV sources routed to a MOTU hardware interface. Experiments in controlling analog hardware from Reason were very successful, so this was the next logical move. I only have a basic understanding of Max, so this is all experimental and will probably sit as one of those never ending works in progress.

How this works

The connection between Reason+Record and mØxr requires an inter application audio routing extension, such as Cycling74 Soundflower, aggregated with your primary audio interface. CV/Gate data is transmitted from Reason+Record to mØxr through Soundflower, while audio signals to and from the hardware interface pass normally. This allows you to trigger a MIDI hardware synthesizer using Reason CV/Gate signals and track the audio back into Record.

As an alternative to soundflower and setting up an aggregate driver, you can also use a purely digital loopback configuration. If your hardware has unused ADAT Lightpipe connections, a digital audio loop from the output to the input can be configured with a short TOSLink cable. (The shorter the better to reduce latency of light). CV/Gate audio data can be routed from Reason+Record to the ADAT lightpipe outputs, and mØxr can receive them from the ADAT lightpipe inputs.

Things you can do

While some work is involved in getting mØxr operational, there are some surprisingly gratifying results. In addition to triggering MIDI synths from a sequence in Reason+Record, Control Voltage pattern devices like the Matrix Pattern Sequencer and RPG-8 Monophonic Arpeggiator can also be used to drive hardware.


Support for mØxr is minimal because there’s no efficient way to tech a system remotely. The documentation is rough, but I’ve attempted to cover the key issues regarding installation and operation. The CV to MIDI conversion process relies on so many different parts working together, so it’s rather difficult for me to provide support without being there in person.

It must be reiterated that mØxr generates a monophonic MIDI stream, so results from polyphonic MIDI sequences are unpredictable. Also, latency varies depending on your driver settings, buffer size, and MIDI configuration. Troubleshooting issues are (somewhat) covered in the documentation.

Download the latest mØxr Documentation

Download mØxr

mØxr is a stand-alone application for MacOS 10.6, and operates side-by-side with Reason+Record duo. Attempts to get it working on Windows have been unsuccessful, but anyone interested in exploring this concept on the windows platform can find the original patches in the MIDIRunner topic in the Propellerhead User Forum

Download mØxr.dmg

- updated 9/18/11 Max 5.1.9
- not tested with Mac OS 10.7 Lion

15 Responses to “mØxr - CV Audio to MIDI Converter”

  1. mikes Says:

    Hi. This is a great app.
    I work 2 weeks with mØxr, but now its not work.

    mØxrquit unexpectedly
    Click reopen th application again. Report send to apple automatically.

    I reisntall mØxr from dog, download new copy, and this problem saved..
    I reinstall sound card drivers, remove all aggregated devices in Audio_midi settings..
    Reinstall Soundflower.
    I can’t run mØxr..
    Its very big problem for me now..

    Who can help me? 2 weeks i work normal. What i can to do?

  2. Peff Says:

    What operating system are you using with this? I haven’t tested mØxr or soundflower with Lion, so I can’t issue any comment about compatibility. Let me check if there’s an update to Max/MSP runtime. I may need to recompile a newer version

  3. mikes Says:

    Hi, Problem was on Macbook White 2008 mb403 with 10.6.6
    Now I buy MBP 13 i5 2.3 with 10.7.1
    In first run of m0xr app all work done..
    in second run app is crashed.. and now when i open - Reopen.. and nothing..
    I download dmg, run downloaded version, and this is problem - please reopen app.. and nothing..

    I reinstall Soundflower 1.5.2 3 times..
    Remove aggregate devices.. and create new.. remove sound cards and install newer versions of drivers..
    nothing help..

  4. mikes Says:

    Its problem from the Log:

    Crashed Thread: 0 Dispatch queue: com.apple.main-thread

    Exception Type: EXC_BAD_ACCESS (SIGBUS)
    Exception Codes: KERN_PROTECTION_FAILURE at 0×0000000000000020

    VM Regions Near 0×20:
    –> __PAGEZERO 0000000000000000-0000000000001000 [ 4K] —/— SM=NUL /Volumes/*/m√òxr.app/Contents/MacOS/m√òxr
    __TEXT 0000000000001000-0000000000379000 [ 3552K] r-x/rwx SM=COW /Volumes/*/m√òxr.app/Contents/MacOS/m√òxr

    Application Specific Information:
    objc[372]: garbage collection is OFF

    As we see - m√òxr.app is problem with name..

  5. peff Says:

    I can compile a new version with Max 5.1.9, however this may not resolve an issue with soundflower under 10.7. Currently soundflower is only supported through 10.6

    One of the fragile points of this process is getting all of the drivers sample rates properly set. Sometimes you need to select the drivers in the Record audio preferences and set the sample rate on the individual drivers (i.e. soundflower (2Ch), soundflower (16Ch), youAudioInterface), and then the sample rate on the aggregate driver.

    If you’re running 10.7, you will probably have to wait until I upgrade, which might be 6 months down the road.

  6. mikes Says:

    Thank You for info.
    I try install 10.6 as second system to try..
    May be its real problem of Soundflower, wait new version.. but last 10.5

  7. mikes Says:

    Hi, problem only in Soundflower..
    If i remove Soundflower, m0xr is work. Then i install Soundflower, restart mac, and work few times.. then m0xr crashed, i reinstall soundflower and work..

  8. peff Says:

    Ok, I’ve updated the mØxr build with Max 5.1.9 which claims to have certain fixes for Lion, however I can’t verify this. This build works fine under Mac OS 10.6.8 with Reason 5+Record 1.5 duo in Snow Leopard.

  9. mikes Says:

    Thank You !!!
    Its work. This updated version help in my problem

  10. peff Says:

    cool! could you send me a screenshot? mail it to peff.com at gmail.com

  11. mikes Says:

    i send them

  12. gummifer Says:

    I’m on Lion and I have the same (or very similar) problem as mikes. The first launch of mØxr went ok, but I didn’t get the midi functionality to work, probably due to some configuration mistake. I cmd + q:ed mØxr to start troubleshooting, but after that I couldn’t get the app running again, at all. I keep getting the “mØxr quit unexpectedly, click to reopen the application again” error, and no amount of rebooting and reinstalling soundflower seems to work. I haven’t tried reinstalling the soundcard drivers yet, though. Do you have any other possible solutions to my problem? I’m so hyped for mØxr, and I would LOVE to get it to work.

  13. peff Says:

    Sorry gumm, you will probably need to wait until I upgrade to Lion and Max 6 before a stable solution can be established.

  14. gummifer Says:

    I finally got it to work! Don’t exactly know why it stopped crashing on launch, but it did. And after some tweaking I got Reason to control my beloved Ensoniq ESQ1 :) A life long dream come true :)
    Of course, it _stopped_ working again after a while, and now I don’t get any sound at all from my monitors, but now at least I know it is possible, even if it is just barely functional.

  15. mikes Says:

    Yes.. app now crashed for me.. and not run.. wait updated version in next year =)

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