(^80) The Official Raspberry Pi Projects Book raspberrypi.org/magpi
ot long after impressing
us with his Raspberry
Pi Looper ‘synth drum
thing’ (magpi.cc/2xZTAXR),
Toby Hendricks (also known as
Otem Rellik) is back again with
another Pi-based musical device.
This time he has constructed
a touchscreen synthesiser
that offers a wide variety of
stunning sounds, modified using
a combination of rotary knobs
and touchscreen control.
“It went through several
iterations before I settled on
the final design,” Toby tells us.
“The original idea was to have
two touchscreens for two-voice
polyphony, but that ended up being
a bit too large, so I went with one.”
Projects SHOWCASE
Frustrated by unreliable iPad music apps, Toby Hendricks built
a homemade touchscreen synth based on a Raspberry Pi Zero
t took a month I
to build and
program
A resistive
overlay is used
(magpi.cc/
2gJSZll)
Sounds can be
stored in eight
patch presets
LEDs are used
to display notes
and menus
A Teensy
3.6 handles
controls and
audio output
Quick
Facts
Rotary knobs control
parameters such as attack,
release, modulation,
detune, and delay
N
TOBY HENDRICKS
Colorado-based musician Toby
performs as Otem Rellik, using mostly
homemade electronic gizmos. His
latest album, unbroken&unheard, is
available from Bandcamp and various
streaming services.
otemrellik.com
Zero debut
While a Teensy 3.6 board is used
to handle the control data, all the
audio – created using a combination
of FM and subtractive synthesis –
is processed in Pure Data on a Pi
Zero. “This was my first project
using the Zero,” says Toby. “I
just wanted to see if I could run a
somewhat simple Pure Data patch
on a Zero without any audio glitches
(and it turns out I could). Size was
definitely a factor: I wanted to make
a really slim, sleek instrument.”
Toby says the Pure Data
programming language is easy to
use. “Once you learn the basics,
you can do so much with audio and
MIDI. It’s a visual programming
language, so instead of writing
code line by line, you create objects
and start connecting patch cables.
It’s great if you are coming from
a non-technical perspective
because everything is so easy
to understand visually.”
Touch the music
While the synth’s rotary knobs
are used to control aspects such
as attack, release, frequency
modulation, detune, and delay,
the main input interface while
playing and creating new sounds is
the touchscreen overlay. Columns
of RGB LEDs placed beneath it
depict eight notes (the scale of
A minor), while the position of
the player’s finger modifies the
sound produced.
FM TOUCH SYNTH
RGB LEDs under the
touchscreen overlay depict
notes and menus
Two push-buttons are
used to access and cycle
through menu screens