Hello everyone, my name is Chantelle Ko, I
am a violinist and a programming musician
with Max MSP. I am currently a Masters
student in Sonic Arts at the University of
Calgary. And I am presenting my research
in how I made TRAVIS II, which is an
acoustic violin that’s augmented with
touch sensors on the fingerboard and used
to expand the violin’s expressive
capabilities. For this version of TRAVIS,
I made it under the supervision of
Dr. Lora Oehlberg whom is an HCI
researcher in computer science and a very
good violinist as well. And I had hired
Aaron Pratte, who is a luthier in Calgary,
to replace the fingerboard with my own.
So I had several objectives. I wanted the
touch sensors to sense all four strings
and the full length of the strings,
have more Force Sensitive Resistors (or FSRs),
and to still use the violin in traditional
contexts without the electronics. I also
wanted to make sure that the strings
aren’t too high and it’s still comfortable
to play.
The two projects that most influenced our
design was Grosshauser’s and
Pardue et al’s. They both had touch sensors either
embedded in or on top of the fingerboard.
If you want to know more about augmented
instruments, please see our paper.
A bit on the history of TRAVIS. It started
as my undergraduate capstone project back
when I was at UBC with Dr. Bob Pritchard.
TRAVIS I had two Softpots on the
fingerboard underneath the G and E strings
and two FSRs clamped to the upper right
bout. Now TRAVIS I had its limitations.
The Softpots only sense the G and E
strings, and they do not sense the full
length of the strings. And I found it
limiting to only have two FSRs to change
presets. My approach was to 3D print a
fingerboard with strips made from
conductive 3D print filament under each
string, run a voltage down the strings,
and measure the variable resistance of the
conductive strips. To test this concept I
setup a circuit with a conductive strip
and spare string. When I connected the
string to different points along the
conductive strip, this showed me that I
was getting a range of analog sensor
values from one end to the other. And now
I just needed to figure out the best
combination of all these variables to make
sure the sensors provide the most stable
data and the largest range of data as
possible. Please see our paper for more
details. Through process of elimination I
narrowed it down to using the Dominant
strings, and 3.3k ohm resistors for all
the strings, except for the E, of which
has a 4.7k ohm resistor.
As for the physical design, I added swiss
machine headers inside the end of the
strips for the wires to plug into. I also
printed various test slots in order to
figure out the proper dimensions for the
strips to be able to easily slide in and
out of. So when I printed the first
fingerboard and got it on the violin,
I found out that it was not strong enough
when I played in the high positions. So I
adjusted my 3D printed fingerboard to be
half the height, and Aaron the luthier
added a piece of flat ebony underneath to
support it. The ebony greatly improves
the strength. But we found that the
fingerboard was still sagging a little
bit, so Aaron made a little wood piece to
prop it up into position. Overall, I think
the most important thing I learned while
making TRAVIS II is do not sand conductive
3D print filament. When conductive
filament is sanded, its surface loses its
conductivity. And I decided to use the
same Arduino as TRAVIS I, the MKR1000.
It was multiplexed for 8 analog sensors.
And the Arduino case is the same basic
design as TRAVIS I, with a few slight
modifications to the dimensions. To
connect the strings, I have a JST
connector hidden underneath the chin rest.
Here is a picture of the same violin,
just with the electronics and wires
unplugged. So if I have back-to-back
rehearsals with traditional violin music
and interactive music, I do not need to
bring two violins with me. So, with
TRAVIS II, I like to have the violin’s
sound pass through different signal
processes and map its sensor data to
change these processes. So if lets say the
violin’s sound is going through a delay,
then the higher I play on the violin, the
more delayed it becomes. I also like to
map different strings to different
processes. So for example if I press the G
string, the sound would be routed to go
through a flange and when I press a D
string, then the violin’s sound goes
through a pitchshift. I’ve found that it
works really well with double stops where
more than one string is played at once.
It also works well in fast passages with a
lot of string changes. Just to give
you all an idea of what I’m describing,
here is a short excerpt from my first
piece with TRAVIS II, Dream State. In this
piece I was improvising, except for in the
ending cadenza. And in this excerpt, I
mapped the Flanger onto the G string.
And here is an excerpt from
Kindred Dichotomy, which was pre-composed.
On the right there is Lora Oehlberg
playing on TRAVIS I. In this excerpt I had
mapped the blue shape in the projection to
change its geometry based on which string was pressed.
So far, I’ve composed
and performed three compositions with
TRAVIS II. Two out of the three were
improvised. TRAVIS works well for
improvisation because, other than
occasionally pressing the FSRs, the
violinist does not have to physically do
anything they wouldn’t normally do
while playing. Cognitively they can choose
to focus on the processed sound that comes
through the loudspeakers and respond to
it, or ignore it and only focus on their
violin playing. As far as modifications
go, there are a few that are more
cosmetic, such as 3D printing with a resin
printer instead of FDM. And using
alternatives for the Arduino and battery
to make it smaller. In my paper I note
different augmented cello projects that
had some troubles with touch sensors on
the fingerboard. So I am curious to find
out if this method with conductive
filament could work on a cello or even a
viola. And I speculate on adding EMG
sensors or flex sensors on a glove and
sleeve in order to track vibrato and
specific fingerings. So whether or not I'm
vibrating can trigger effects. Scrubbing
samples is something I’ve done in past
compositions with TRAVIS I, but I have not
yet explored it with TRAVIS II. I have
used colour changing LEDs and DMX lights
before for other projects and I think it
would be fun to have them be controlled by
TRAVIS II.
Thanks for listening to my presentation.