Alternative Cajon design ideas for DMI

David Creasey has pointed out that perhaps the Cajon in its well known "box that you sit on" form is slightly awkward to play. I think that this is perhaps true especially considering that players will typically lean back and balance on the instrument in order to better reach the playing surface, which still requires bending down some what. This also certainly confirms some worries I had regarding the placement of any transducers I should choose to include, which I would likely place on the front playing surface (the really any of the surfaces would be about as awkward). The problem is I think that reaching down in order to strike an area of the tapa is OK but reaching down to perform a gesture on say, a linear position sensor, would be much more awkward especially if one was trying to achieve really fine control. Of course an important advantage often cited regarding DMIs is that we are not necessarily obligated to certain designs when constructing the instrument. Specifically, the seperation of control interface and sound production mechanism inherent in DMIs means that the sound production mechanism does not dictate the physical properties of the controller. For example an acoustic stringed instrument needs to be of a specific length in order to hold strings of the correct length to achieve their desired pitch (more correctly it is a balance between string length, thickness and tension). With DMIs there are no such obligations, we can produce any sound from any thing. (although actually I'm beginning to think we are not necessarily completely free of obligation since for example inclusion of one or several loudspeakers immediately requires an object of a certain size, the same for housing internal electronics and for providing transducers of a certain shape, length, size. It seems to me that obligations are perhaps reintroduced when thinking about designing GOOD or EFFECTIVE or EXPRESSIVE DMIs given the results of research. That's another argument for another post though.)

Keeping with the original inspiration for a Cajon-inspired controller (easy construction, loudspeaker placement etc) David has suggested I might try looking into other types of drum with the same family. Specifically the Cajinto. From the same website however I have found a section called "Cajon Compact" under which are the Cajon Comparsa and the Cajonito. Both of these drums closely follow the design of the Cajon in that they are both boxes with a hole in them but they are much smaller and are shown held between the legs like a bongo. The Cajonito is the smallest of the two. I think I would opt for one of these two over the Cajinto since I like the way they encourage a lot of bodily contact with the instrument, which I think would really allow the vibrotactile feedback element to do its job well. I'm not sure which of the two I would choose however. The Comparsa is nice because there's plenty of room for all the electronics on the inside and plenty of room to play on the top but the Cajonito, with its smaller size, is perhaps comfier to hold and easier to play.

All of these instruments are listed on the percussion website shlagwerk.com. This is a brilliant website for my needs since it has an extensive selection of instruments from the Cajon family, it has video demonstrations of all of them and it gives their dimensions which is one less concern when it comes it building!

There are two other options which come from the percussion company Meinl. The first is the Bongo Cajon. This is a smaller rectangular Cajon designed to be played either between the legs or on the lap. The bottom side is left open for sound output and interestingly the inside of the drum is split into two sections with a piece of wood, one being bigger than the other. This allows the player to get a low and a high sound out of the tapa. I think this could be quite a nice playing style to emulate in my DMI by some one measuring playing position from left to right. This could not only affect pitch but also some aspects of timbre which would give a nice one-to-many mapping associated with the best DMIs. Would also be interesting to think about the y-axis position.

The second option from Meinl is the Palito. This instrument seems similar to the Schlagwerk Cajonito, though seems to give a different sound. Also the Cajonito seems to be larger. I think I would probably opt for one of the above Schlagwerk designs above the Palito since I need to think about practical space considerations regarding the internal electronics, particularly the loudspeaker (not to mention amplifier and power supply which are another worry all together).

Listed below are some basic resources i've found so far:

This is a project page made by a guy who built his own approximation of a Bongo Cajon. There's some basic instructions along with construction pictures and a demonstration video. I don't really like the finished article. It seems rather big and awkward to play. Also the method of producing two seperate tones from the drum does not seem as effective as the more usual technique mentioned above.
Demonstration video of the Meinl Bongo Cajon
A second very similar demonstration of the same instrument by the same guy
Demonstration video of the Meinl Palito

Cajon Drum Prototype

Over the last few days my father and I have been working on a prototype cajon drum using designs and tutorial videos found on the internet (the sources for which are listed in a previous post), as well as some improvisation and customization on our part based on the materials available to us as well as some mistakes made.

The drum we've made is very much a practise run and there are certain aspects of its design that did not go so well at the time of building. But, importantly, there have been lessons learned from the mistakes and we plan to improve on the design and build a superior version of the drum.

In that respect building this initial version has been extremely beneficial. Although the drum is designed to be purely acoustic according to the traditional design, and so other issues such as electronic have not yet been addressed, its building has highlighted that creating a box of this kind is not as straight forward as first thought and there's plenty of room for mistakes.

Despite all that, the box functions perfectly well as a drum. It is possible to find different tones across the playing surface (tapa) and to combine these into interesting rhythms. Most importantly, its a lot of fun to play.

Here are some pictures of the design and basic playing position:

In this last one you can make out that the box is slightly tipped backwards during playing to allow more comfortable access to the tapa.

Design details:

• 12mm thick plywood for sides, back, top and bottom
• Joined with wood glue and nails (using nail gun)
• 3.6mm thick plywood for tapa
• Joined with screws

I'll write up some detailed design details for the next version since its likely to be the finally and should have no mistakes.

I now need to decide on some design details relating to the electronic version including:

• Loudspeaker size, since this will inform the required diameter of the "sound hole" in the back where the loudspeaker will be mounted.
• I know loudspeaker size will also affect the required size of the box (in terms of volume) but I'm not sure how. I may have to ask David Creasey about this...
• I need to make sure that I have easy access to the inside of the box to place the electronics, this should be possible through unscrewing the tapa.
• I need to think about issues around transducers and their placement for my DMI since I haven't actually got a concrete plan yet.

The Importance of Parameter Mapping in Electronic Instrument Design - Andy Hunt; Marcelo M. Wanderley; Matthew Paradis

The Importance of Parameter Mapping in Electronic Instrument Design - Andy Hunt, Marcelo Wanderley, Matthew Paradis

A rather brilliant article for several reasons. To start this article serves as some thing as a reference point for many major research projects into mapping in DMIs and as such will be very handy to refer back to later should I need inspiration for this stage. Also the article uses both objective and subjective treatments to argue that many-many (complex) strategies provide much more intimate and expressive music making experiences. One interesting example is that of the "accidental theremin". The paper also provides a better description (in my opinion) of the results and conclusions presented in Instrumental Gestural Mapping Strategies as Expressivity Determinants in Computer Music Performance by Rovan et al.

Most Important/Interesting Publications on DMIs

In this post I've collected what I consider to be the most important publications on DMIs that I've found with regards to my project. I've posted them here for quick reference and also in order to filter out the most useful items for printing and annotating.

• Gestural Control of Music - Marcelo M. Wanderley
• On the Choice of Transducer Technologies for Specific Musical Functions - Marcelo M. Wanderley et al
• Towards a Musician's Cockpit: Transducers, Feedback and Musical Function - Roel Vertegaal (second entry)
• Gesture - Music, Claude Cadoz
• Mapping Performer Parameters to Synthesis Engines - A. Hunt and M. Wanderley
• Expressiveness and Digital Musical Instrument Design - Daniel Arfib et al
• Physical Interface Design for Digital Musical Instruments - Mark Marshall
• Digital Lutherie - Crafting Musical Computers for New Musics' Performance and Improvisation.
• Towards a Model for Instrumental Mapping in Expert Musical Interaction - A. Hunt, M. Wanderley, R. Kirk
• Sensor Choice for Parameter Modulations in Digital Musical Instruments: Empirical Evidence from Pitch Modulation - Max T Marshall et al
• Musical Vibrotactile Feeback - David M. Birnbaum
• A Consort of Gestural Musical Controllers - Joseph Malloch (first result)