Sources for Electronic Components

The following are some resources for electronic components suggested by David Creasey since the university has accounts with the companies and is able to purchase modestly priced items on behalf of students:

Farnell (http://uk.farnell.com/)
RS (http://www.rswww.com/)

Farnell in particular has a range of components from power amplifiers and loudspeakers to sensors and transducers.

Also of interest is Studio Spares (http://www.studiospares.com/page/home/)

Updated Controller Design Spider Diagram

Above is an updated version of the previously posted spider diagram to show key aspects, issues, ideas and potential solutions regarding the design of the controller. The key area that has been changed is the "physical design" branch which has been updated following the completion of the cajon comparsa prototype. It therefore discussions some potential solutions and issues presented by the new design and compares some of its aspects with those of the original cajon prototype.



Key:
Orange - potential solutions
red - potential issues

Cajon Comparsa Prototype

This post introduces the second prototype drum to be created for this project. This model is based on the Cajon Comparsa. The dimensions for the drum were taken from this website.

Although some lessons were learned from building the Cajon (such as not using a nail gun) and the new comparsa model is undoubtedly improved from the cajon, there were still some mistakes and plenty of tricky areas. Again my father helped me in the construction of this drum and he has years of experience with woodwork and a collection of the necessary tools and plenty that makes things easier (ie belt and orbital sanders, routers, jigsaws). This is making me think that perhaps if possible I would like to use one of the prototypes that we create to at least begin testing out the electronic and synthesis systems and possibly for inclusion in a final deliverable artifact. This is because if I were to attempt to build a drum on my own in order to gain credit for the design it would likely be time consuming, difficult and potentially expensive and it seems like perhaps, although clearly the ergonomics of the controller are important, for this project I need to focus more on other potentially more difficult areas. This is especially taking into account the legendary difficulty of the mapping stage. Mark Marshall for example said in his e-mail that in his DMI projects he has spent by far the most time fine tuning the mapping.

The comparsa is perhaps a little too tall to play on one's lap since for me, my arms are forced to bend upwards at the elbow from my waist to reach the tapa which is not particularly comfortable.

These issues suggest that perhaps a design closer in dimension to the Cajonito or even the Palito would be more suitable. I have some reservations about this though since I would like as much of the electronics to be housed internally as possible and obviously the smaller the controller is the less this is possible. Naturally however more internal electronics is going to mean more weight which could be a problem if the player is trying to hold the instrument with their legs.

Here are some pictures of the Comparsa:

As can be seen in the first few pictures the comparsa (according the demonstration videos presented on the Schlagwerk website) is typically held with opposing corners gripped between the knees and the tapa angled slightly downwards, with the sound hole facing away from the player. Also visible in the last few pictures are the marks from the wood filler used to fill up holes and chips created in the wood, evidence that putting the thing together is a little tricky.

Design details:

• 9mm thick MDF for sides and bottom
• Joined with wood glue and screws, screws have been counter-sunk
• 3.6mm plywood for tapa
• Joined with screws, counter-sunk
• 5mm sound hole
• All sides curved using router
• Coated with wood stain for an attractive finish

It was decided to use MDF for the body of the instrument since its cheaper than plywood. Also important to note that the quality of the wood is unimportant from a sound point of view since the sound will be synthesized, therefore cheap but sturdy wood can be used. Having said this the MDF presented as many problems with splitting as did the plywood. Also the MDF was thinner than the plywood at 9mm instead of 12mm. This size was chosen to make the instrument lighter, considering it was to be held between the legs.

Commercial Electronic Hand Percussion

In an attempt to find a little inspiration I spent a little time searching for commercial products that were of a similar concept as my curent Cajon-inspired DMI idea. I was mostly interested in aspects of ergonomics, design and control as well as sensing technologies. I first found the Roland HPD-10:

Roland HPD-10 product demonstration
Official product page

The HPD-10 is based around a set of 10 drum pads. Each pad is pressure sensitive and are able to detect the position of the strike on their surface.

Of more interest to me is the Korg Wavedrum:

Korg Wavedrum product promotion
Korg Wavedrum official product page

The Wavedrum is especially interesting for two main reasons. Firstly the instrument does not use a typical drum pag style interface. The instrument actually uses a real drum skin as the main portion of its interface. The skin is surrounded by a rim with a control interface at the top. The instrument consists of four discrete triggers; two are part of the rim, one is just below the control interface and the fourth is the drum skin itself. The use of the skin should instantly give the instrument great tactile feedback when playing with hands or sticks. The second reason is the sensing method. The skin and rim are equiped with pickup sensors allowing the vibrations of the instrument in response to strikes to be sensed. These signals are then used as the input to the synthesis algorithms. I can imagine this allowing an amazing sense of connection and intimacy with the instrument since any conceivable interaction with its playing surface will have an audible effect which is unique each time for each player as well as a rich amount of nuance (given an appropriate and effective software strategy which I'm positive is used here). As well as this, the skin is equiped with a pressure sensor to pick up extra detail from the player's attacks. This is similar to what I had in mind for my own DMI with my idea to use piezo microphones to monitor the vibrations of the instrument body (inspired by a conversation with Hugues Genevois). The addition of pressure sensing is also an appealing idea.

There are two things however that both these controllers seem to lack and they are vibrotactile feedback and sound localization. Neither controller (as far as I can tell) has any kind of built in sound production and would rely on external speakers, removing the immediate sense of presence of an acoustic instrument. Also, neither instrument provides any kind of vibrotactile feedback system even if only as a result of active internal sound feedback. Although I can imagine this situation being better in the Wavedrum since it incorporates a much more freeling vibrating membrane (as apposed to pads) I still can't imagine it compares with being in bodily contact with say a cajon and feeling it vibrate in response to your gestures.

The Wavedrum especially then provides some interesting sensor applications as well as some evident areas that I can attempt to work on to make my DMI a little more individual

The Vodhran DMI by Mark Marshall et al

Three articles describing The Vodhran are available towards the bottom of Mark Marshall's publications page:

Controlling the Virtual Bodhran - the Vodran - R. Bresin, S. Dahl, M. Marshall, M. Rath and B. Moynihan

The Virtual Bodhran - Design and Development of a Virtual Musical Instrument - M. Marshall, B. Moynihan and M. Rath

The Virtual Bodhran - The Vodhran - M. Marshall, B. Moynihan and M. Rath

I include these articles here because I thought the Vodhran may be conceptually similar to my Cajon DMI but on reading the articles its possible that they're not so similar, however they're still examples of an interesting DMI. The most usual article seems to be the first one, which gives the most concrete description of the various applications of the Vodhran from the software to the controller.

One application of the Vodhran uses Max Mathew's radio baton to measure the distance and position of the each end of the beater from the antenna. Another uses a gesture tracking system to extract details about the player's gestures such as velocity and acceleration. The application conceptually closest to the ideas I have at the moment seems to be the one involving the ddrum (a MIDI drum-pad with velocity sensitivity and aftertouch parameters):

" In addition to the control devices described above, the ddrum [6]
was used to play the sound model of the Bodhran (see Figure 2 A).
The ddrum is a commercial available electronic drumpad and the
MIDI velocity out from the control unit was used to excite the
sound model. For the pad used there was also MIDI poly-aftertouch,
which was used to control the dampening of the model. The ddrum
is a nice interface to play the model because of it’s tactile feedback
to the player and the lack of cables to the sticks used for playing. "

Note the advantages stated regarding the ddrum's passive tactile feedback.

These articles seem to demonstrate three main ways that I could approach handelling gestural interfacing for this project:

1. Monitor the position of the beater/s (hands, sticks) with respect to the controller itself
2. Use gesture tracking to extract indirect features of player's gestures for control (ie velocity)
3. Monitor the state of the controller itself for strikes

Project Deliverables

Key:
red = essential
green = desirable
blue = optional

Above is a diagram showing the deliverable items for this project. This has been created in order to break the project into its constituent parts and, more importantly, to show which areas should be concentrated on most heavily and which areas can be left in case of difficult deadlines. Not only this but it also helps to identify areas of the project which could be developed if time allows and also suggests some ideas for future work/projects, which will be useful when writing the report.

As it stands this diagram is only a first draft and I will likely extend and add to it as I begin to work on each of the individual parts it shows.

Control Parameters for Musical Instruments - Daniel Levitan

Controll Parameters for Musical Instruments: a foundation for new mappinds from gesture to sound - Daniel Levitan et al (third result)

This is a brilliant paper. It offers up a new and detailed way of disecting a particular musical tone into its constituant parts, defined as selective cognitive preconditions, beginning, middle, end, terminus. It presents in details the choices we can make of how to execute each portion and what sonic results they will have and then goes onto combine these principals into the manners in which we can execute a tone as a whole, showing a decision path. According to the authors:


" The essential points are to
employ controls that are both consistent with how the
sound might have been created in a traditional musical
instrument (so as to exploit principles of cognition and
the mind), and to inspire designers to think about the
control of sound in ways that go beyond those employed
in traditional musical instruments (which are constrained
by physical, but not always cognitive factors). "

The concept of designing DMIs that operate in such away that their sonic responses to our gestures correspond to our pre-existing cognitive expectations is an interesting one. Another interesting thing about this article is one of the motivations of the authors:

" Our approach is the
consequence of one bias that we should reveal at the
outset: we believe that electronically controlled (and this
includes computer-controlled) musical instruments need
to be emancipated from the keyboard metaphor;
although piano-like keyboards are convenient and familiar,
they limit the musician’s expressiveness (Mathews
1991, Vertegaal and Eaglestone 1996, Paradiso 1997,
Levitin and Adams 1998). This is especially true in the
domain of computer music, in which timbres can be created
that go far beyond the physical constraints of traditional
acoustic instruments. "

Physical Interfaces in the Electronic Arts - Bert Bongers

Physical Interfaces in the Electronic Arts - Bert Bongers (first result)

A fairly informative and interesting paper split into three main parts. The paper starts with an introductory history of the ergonomical aspects of the design of instruments. Several models are then presented of interaction in performance arts along with some practical examples. The final part gives a fairly detailed account of various kinds of sensors, including some technical aspects to their design and operation, and lists examples of DMIs and installations which have made use of them.

Tactile Audio Feedback - Chris Chafe

Tactile Audio Feedback - Chris Chafe

Article arguing that vibrotactile feedback can help to improve performer control in musical instrument playing situations

Principles for Designing Computer Music Controllers - Perry Cook

Principles for Designing Computer Music Controllers - Perry Cook (third result)

This paper presents a list of guidelines/advice for designers of computer music controllers. They are demonstrated through descriptions of several controllers of various categories.

Remutualizing the Musical Instrument - Perry Cook

Remutualizing the Musical Instrument: Co-design of Synthesis Algorithms and Controllers - Perry Cook (third result)

Particularly interesting in this article is a presentation of a brief history of the concept of separating control interface from sound production mechanism (going back to the first organs) along with a proposition of reasons why this has lead to lack of intimacy:


" The major flaw in the controller/synthesizer paradigm is
the loss of intimacy between human player and instrument.
I pose three primary reasons (lacks) for this intimacy loss:
• Lack of haptic feedback from the controller/instrument to
the player. Haptic (combined senses of touch, including
skin vibration and pressure, and the muscle senses of
motion, position, and force) feedback has been increasingly
addressed in musical interface research projects.
Commercially, the most successful haptic systems are electronic
keyboards that copy (passively, through weights and
levers) the feel of piano keys.
• Lack of fidelity in the connections from the controller/
sensor to the generator, primarily delays and distortions
in response to gestures. “Distortion” here refers to any
response that does not meet some usual, learnable, or
repeatable expectation.
• Lack of any sense that sound comes from the instrument
(the controller) itself. More generally, this is a subset of a
larger feeling that no meaningful physics goes on in the
controller. Trends toward larger concert venues, greater
amplification, and larger loudspeakers have consistently
worked to diminish the importance of the actual acoustical
instrument sound. The aesthetic influence of this has
been great, most importantly for the player and composer,
and shows profoundly in the musical results (Trueman,
1999). "

Finally a presentation of some DMIs which have been designed in an attempt to remedy these issues. Notably these instruments have followed a process where the synthesis and controller designs have been created in parallel with each other and have informed each other throughout. Included is the previously seen BoSSA system, some hand percussion physical model controllers and the SqueezeVoxen, a series of accordian-inspired instruments (Bart, Lisa, Maggie and Santa's Little Helper) which seem to have designed as a family, like the T-Sticks.

Of particular interest is the Nukulele and the Nukulele'elua which bear striking resembelence to some of the very first design ideas I had for my DMI.

Controller Design Spider Diagram

On the advice of David Creasey I've created a spider diagram which attempts to break up the task of creating the actual physical controller into constituant issues and problems. Above is a first draft of this diagram. Hopefully through revising the diagram I can begin to address a few of the problems it identifies. I may have some more answers to the questions once I've tried the new controller designs mentioned in the previous post. I will be able to address many questions once I begin playing with electronics at university.