Saturday, February 5, 2011

Sampling and sound design with Mobius

Lately, I’ve started exploring the use of the Mobius looper as a sampler to create new and interesting sounds to be triggered by my guitar controller. By doing this, I hope to recreate, in a live setting, a technique I developed in the studio that allows me to create a pitched sound by taking a very short part of a recording (usually vocal) and repeating it many times. I like to think of this as a type of granular synthesis, although, strictly speaking, it's not.

Start with a short loop

The first step is to create a short loop in Mobius. The best way to achieve this is to use Sustain Record, since this function only records when the button is activated and automatically stops recording when the button is released. At this point, you should have something that might sound like this (if you were to sample my voice).

Short loop:

Interesting, but since the repetitions aren’t fast enough, it doesn’t sound like a musical note. There are two ways to make the repetitions faster. We could increase the Rate of playback, which increases the speed at which the loop is played, or we could make the loop even shorter, thus increasing the frequency of repetitions. There are many ways of doing this, but my favourite so far makes use of the loop windowing script Jeff Larson put together. Activating this script selects a single subcycle to play back. Using the script again selects another subcycle. In this way, a single loop can yield many different sounds. Here’s how things sound at this point using both of these options on the above loop.

Well, at least we have a tone!

Sound design

There are countless possibilities to further manipulate these sounds, both in and out of Mobius. For now, I’ve limited myself to three plugins: Discord3, Chopitch and UpStereo. Discord3 is where the meat of the sound design is taking place. It is a formidable effect that allows me to introduce a lot of complexity to any sound. While Chopitch adds character to the sound, its primary role is to shift the pitch of Discord3’s output according to the midi signals sent from my guitar controller. The last plugin, UpStereo, increases the sound’s presence in the mix.

There are also some sound design possibilities within Mobius itself. For instance, the sample can be changed by sampling over the existing loop using Replace (with no Secondary Feedback). When this is done with a rate-shifted short loop, the results are rather interesting. Because the repetitions are occurring at a sufficient frequency, we retain the perception of a tone, but the sound in the loop is no longer rate-shifted and retains more of its initial character.

Another option is to briefly overdub the loop to add further complexity to the sound. However, it is important to pay close attention to the Secondary Feedback setting while doing so, since things can easily get too loud when overdubbing such a short loop at full feedback.

It’s interesting to try out some functions and scripts to hear their impact on the sound. Halfspeed, as expected, will lower everything by an octave. Using the previously mentioned loop windowing script on a rate-shifted loop will produce a wispy high tone. Using a version of this Auto Reverse script will add a lot of ‘dirt’ to the sound.

Sound examples

These examples all start from the same short loop recorded in Mobius.

Example 1: Loopwindowed ->Discord3 -> Chopitch -> UpStereo

Example 2: Loopwindowed ->AutoReverse  ->Discord3 -> Chopitch -> UpStereo

Example 3:Loopwindowed ->Rate+24 -> Discord3 -> Chopitch -> UpStereo

Example 4:Loopwindowed ->Rate+24 -> autoReverse -> Discord3 -> Chopitch -> UpStereo

Example 5: RateShifted -> Discord3 -> Chopitch -> UpStereo

Example 6:RateShifted -> autoReverse -> Discord3 -> Chopitch -> UpStereo

Example 7: RateShifted -> LoopWindowing -> Discord3 -> Chopitch -> UpStereo

Example 8: RateShifted -> Overdub -> Discord3 -> Chopitch -> UpStereo