BPM Trigger

Hey all, ER-301 newbie here. I’m trying to set up a trigger for an external tap tempo based on some incoming audio. I have the audio going through a lowpass EQ module, then that’s fed into an envelope follower.

I’m not really sure where to go next. I know some units have triggers that can be fired at a certain threshold—setting that to an appropriate level on the envelope follower seems like the next logical step. Something involving an ADSR seems like the next step, but I haven’t quite figured it out yet. Any clues?

Are you trying to clock an external module’s tap tempo feature, or a process within the 301 somewhere?

The 301 does not have DC coupled outputs FYI… so you can’t properly send CV signals out of the module, only audio (realistically).

If it’s for something internal, You’d add a Tap Tempo Unit, and then assign the tap to your clock signal.


The former. That’s unfortunate to hear, I didn’t realize that, considering there’s an offset unit, etc. I’m building a compact setup and was hoping to replace some signal generation units with an ER-301, in addition to doing some sound processing. Looks like I need to go back to the drawing board…

Ahh I can imagine your disappointment over this misunderstanding… I didn’t answer because I was trying to work out what you meant, but Neil worked it out, I didn’t imagine you were thinking to route DC out as the outs are AC.

I hope this doesn’t break your dreams too much and I strongly encourage you to read this forum thoroughly to check out what is possible with this awesome module because disappointment should not be a word that is readily associated with it :slight_smile:

The CV signal generation is still there for internal use and the possibilities are staggering! It’s increasingly likely you can still do what you want anyway, or at least get close with a bit of imaginative thinking.

Perhaps start with the topics with the customunit tag in the menu at the top of the forum home page…

You could always feed an audio output into a module like Mutable Instruments Ears to generate a gate + envelope. The ER-301 can replace a lot of other modules and Ears is only 4hp, so they work nicely together in a small setup.


I was a little disappointed but not very much so. The ER-301 has so many other uses that justify its existence, even in my compact setup. Sampling and sample playback, especially. I’m relatively new to the modular world, and was a bit shocked to see the state of the art for sample-based devices in the modular context. They offer very basic functionality and are very inappropriately priced. The ER-301, on the other hand, very gracefully handles sample based tasks and the sky is the limit.


i use the tap tempo to clock external stuff on an otherwise empty chain, it works well. but lfo’s and envelopes can’t be routed outside.

I had already considered picking up an Ears for other reasons, it does seem like a very useful unit for the size. Thanks for the suggestion.

I got to try out this method today. Input > EQ3 > Limiter with pre-gain > Envelope follower with a goodly amount of attack and release > another limiter with pre-gain > Trigger with moderate threshold on for a Tap Tempo unit > My external tap tempo.

It’s reasonably reliable at varying input volume levels and across different kicks. Like most other “unintelligent” tap tempos it is very susceptible to triplet kicks or other odd transients in the bass registers.

I’ve searched for a decent solution to this problem in the modular world for a few months now, and simply found nothing. This is very surprising to me. I understand it’s not difficult to clock something with a computer, midi, or other modular sound source in the mix, but there is simply nothing out there for tracking/clocking audio.

Hopefully we get an SDK for developing our own modules soon. I know Lua and have some decent algorithms on hand for doing reliable BPM tracking. I am a professional developer so I know the challenges of releasing an API too soon and supporting it over time. At the same time, I would love to get my hands on it at some point!

Final point, it seems the tap tempo module is capable of producing a PWM-like signal reliably. I assume this is using the same techniques that synthesizers use to approximate square waves. I don’t see any reason that the ER-301 shouldn’t be able to generate triggers using this same technique (they are just short duty-cycle pulses after all). No DC component is needed. I don’t know enough about LFO and envelope generation to comment on those but they seem doable as well. Perhaps someone can educate me on why the ER-301 wouldn’t be fit for those tasks.

I manage to clock my prophet 6 sequencer with the tap tempo unit also.