Music on Tablets – Elastic Drums and WretchUp from Mouse on Mars Instruments

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A whole new world of sound generating and modifying possibilities are available today with tablet computers and smartphones.  Here we show you some of the many ways that be accomplished.


by Warren Burt, July 2015


Today we look at two new apps which offer a unique range of sound-design possibilities, providing sound fun for the distortion-minded, and at extreme settings, offer a wild sonic ride to the outermost limits of noise and distortion.

WretchUp and Elastic Drums are two apps from Mouse on Mars Instruments, which was founded by the Berlin-based Mouse on Mars duo (Jan St Werner and Andi Toma), but which now involves more people than the original two. The technical director of the group is Oliver Greschke with some help on
PureData patching by Matt Davey.  They’ve been working in the public domain programming environments Pure Data and libPD, developing iPad and iPhone apps.  (Given the ease of programming in Pure Data, this is a development we can only applaud, and hope that it portends a whole new set of apps from many more developers!)

WretchUp is a “simple” delay with pitch-shifting effect, while Elastic Drums is a rather interesting “drum” synthesizer and sequencer, which has the potential to evolve into one of the most powerful little “percussion” apps around. 

First to WretchUp.  It’s for both iPhone and iPad, and it processes either an incoming signal or a loop that you can record internally.  The main front page features only 5 controls, but they’re big, and allow easy control, even without having to have your eyes focused on the screen.  This reflects the fact that the app has been tested in live performance a lot.  Ease of access is paramount here.  Auxiliary controls, which could slow things down in live performance, are placed on separate pages, accessed through down-arrows on the bottom of the screen.

The five controls are Base Frequency (the amount the delay will be frequency shifted), Delay Time (from instantaneous to about ½ second), Feedback 1, Filter (a fairly subtle effect), and Feedback 2.  The two feedback controls seem not to be set into a kind of linear relationship with each other so, especially at higher settings, sometimes fairly unpredictable results can be had.  I don’t know if the developers are aware of this, but this kind of semi-unpredictable feedback loop circuit was pioneered by the American experimental composer David Tudor in the 1970s, and the sound of this app is squarely in the lineage of his work.

The first of the two auxiliary pages is “Live Input” accessed from a down-arrow at the bottom of the page, only after the tab for Live Input is touched.  This page has two sliders and a switch on it.  The top slider is the volume for the live input, and the lower one is a balance called “effect mix,” with only the live input on the left and only the effected sound on the right.  Below these is a switch, which can either allow touching the controls to turn the sound on and off, or having sound always coming in and turned on.  A note though, for the second mode – even if you have the “always on” mode selected, when you first turn on the app, you still have to touch the screen to activate the app.

The second auxiliary page is the looper.  You activate recording by pressing and holding the “Rec” button.  This will record up to 15 seconds of sound.  (I’d like more, but then again, I ALWAYS want more.  Still, 15 seconds is at least better than 2 or 3 seconds).  Speed of the loop, both faster and slower, is controlled by a big circular control, and direction by two arrows underneath that.  Balance of the loop and the effect is controlled by the horizontal slider at the top.

And that’s it.  No MIDI-learn, no external control, none of that.  This is a module that is just designed for live performance, and a kind of “non-numbers-oriented” live performance at that.  The graphics are quite charming, and give a good indication of where things are, but exact reproducibility is not the app’s point.  This is an app which is best designed for improvisatory use in live performance, although working in the studio, with the sound recorder always running, would also yield a lot of interesting results.

What does it sound like?  The pitch shifting is fairly grainy (that’s a feature, not a bug) and at lower levels, Feedback 1 is a predictable “number of echoes before fading out” control.  It’s when you get higher levels of feedback with the 2 controls interacting that things begin to get really interesting, especially if you’re manipulating the Pitch Shift and Delay Length controls while doing that.  Then you begin to get unpredictable sequence like patterns of gliding tones, shreds of your original sound, and lots of nicely shaped noise.  Some of the non-linearity of the system can be shown by the fact that when I played a single piano tone into the unit, with Delay Length set to full, and Feedback 1 set to about 2/3, and Feedback 2 set to about 1/3, I heard my original tone, then the pitch-shifted tone, then the pitch-shifted tone repeating at a softer volume each time, but after a few repeats, the pitch of the pitch-shifted tone began to vary as well, in an unpredictable manner.  And each time I played a single piano tone, and listened to the app with these settings, I got a slightly different (sometimes radically different) set of pitch variations in the later part of the delay fade out.  Well worth the $3.99 price, this is an app which, if you’re improvisationally-minded, and a fan of distortion, will tickle your fancy.

An order of complexity, and predictability, higher is Elastic Drums, by Oliver Greschke and Matt Davey.  Billed as “an iOS app with 6 channels of synthesized sounds, a step sequencer and 4 effect channels, all tweak-able in an elastic way,” it’s all that, and more.  The synthesized sounds are represented by “10 different percussion synth engines (kick, snare, hihat, clap, tom, wobble, fm, fm4, square, grain),” each with 12 modifiable parameters.  The manual for the app, easily accessible from within the app, lists what each parameter does for each synth engine, and  the presets available with each synth engine provide quite good conventional drum machine sounds.  But the range of all of the parameters is so large, and the programming possibilities for each synth engine are so flexible, that this strikes me as more an app for those who want to explore the wide range of synthesis possibilities available than as simple a “drum machine” app.  And except for the hardwired limitation of all the synth engines having sharp attacks (these are “percussion synth engines” after all) the range of possible sounds, especially with the “fm4operator” synth, is immense.  Each of these synth sounds plays at only one pitch, unless you automate the pitch control (all front panel controls on the Instrument page can be automated), or control it (the pitch control) from an external source.  In other words, we’re not talking MIDI pitch control here, except as a by-product of controlling the pitch control with a continuous controller.  One can also set velocity to control any of the synth parameters, so one could have a MIDI note-on signal (from an external keyboard, say) triggering off a sound, with the velocity of that key being what controls the pitch of that particular synth engine.


With ten different percussive synth engines to choose from, for each channel of the six-channel sequencer, the range of timbres it can produce is pretty amazing.  One thing I noticed is that if you’re programming the twelve parameter knobs for one kind of synth engine, and you shift to another synth engine, the knobs retain their same position, even though they now control different things.  This could lead to all kinds of explorations as to what a particular setting of knobs produce with different engines.  The sequencer can have sixteen patterns in it, and each pattern can save all the parameters for each synth engine on each track.  In other words, you can have a completely different set of timbres for each sequencer pattern, should you so desire.

On to the sequencer.  Each pattern is a grid of sixteen slots by six channels.  Although the six channels are shown immediately below each other, implying (as they normally would) the six channels playing in sync, each channel can have its own tempo offset.  At the moment these are simple multiples of the main tempo – .5, 1.0, 2.0 and 4.0 – but I am told by Oliver Greschke that an update to be expected in August will have a much wider range of tempo multiples available for each line.  This means that you can have percussion lines moving at very lovely and strange tempo relationships.  I hope he continues to develop this feature in the future.  I’d love to, for example, explore such traditional Mexican tempo relationships as e/pi between different rhythmic lines of a sequence! (Traditional Mexican?  Yes, if your idea of Mexican tradition includes a composer like Conlon Nancarrow! )

The six synths can each be triggered by an external MIDI note-in, and each line can output that particular MIDI note as well.  At the moment, those are only MIDI note numbers 37, 38, 39, 41, 42 and 43, but Oliver Greschke has told me that the August update will allow any MIDI note numbers to be assigned to each of the sequencer’s channels.  MIDI learn is expected to be implemented as well.  For the moment, there is a rather nice mapping of MIDI ccs to each parameter of each channel’s synthesizer.  I’ve already connected my Korg NanoKontrol2 to Elastic Drums using these mappings and the result has been quite a lot of fun.


Although the sequencer grid is sixteen slots wide, a control allows you to have individual lines of any length up to and including sixteen steps.  So phasing lines are quite possible.  There are sixteen slots for individual grids on the Arrange page.  Each slot can hold a pattern and all of the parameters for all of the synthesizers.  You can sequence through the patterns automatically, or manually on the Arrange page. 


Also, on the Arrange page is a Mixer for convenience and for routing individual channels into particular effects, and Master Effects controls for the sequencers and their instruments.  Of these effects, the Swing control is remarkable for allowing a swing pattern to go across 2, 4, 8 or 16 notes, rather than just 2 notes (lots of potential there), and there are some very nice audio effects, like Freeze and Delay.  In fact, if you run Elastic Drums into WretchUp through Audiobus (as shown in the previous photo), and you have the Delay in Elastic Drums happening and feeding into WretchUp, you can get some incredibly complex and unpredictable delays happening with the processing of the delays from Elastic Drums then being delayed by WretchUp.  Fun like this doesn’t come along very often.


“But wait!” As the late night TV salesman says, “There’s more.”  There is an Effects page, where the behaviour of up to four of the effects (eleven mono and nine stereo) can be automated as well.  So with automatable controls on the synth engines, patterns that can be changed manually or automatically, automatable effects, and Master Effects like Swing, Stutter and Delay, Elastic Drums is much more than a simple drum machine app.  It is, in fact, a unique and powerful synthesis system that can generate a wide range of patterns and sounds, and can be used, especially in live performance, in a very wide variety of situations.  And with the upcoming additions in the August update, what is currently a very powerful system will become even more subtle and capable of advanced musical expression.  As well, the app is completely AudioBus and InterAppAudio friendly, so it can become a completely integrated part of your iOS composing tool kit.  Highly recommended, and very high on the fun factor.  At $9.99, this is a steal.


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