Following on from this post.

On Monday we met to discuss the first prototypes of the two instruments we wanted to explore as detailed in the previous post.

The Filter Box

We took a look at the first Filter Box prototype as seen in the pictures below which was set-up in a temporary box for testing of the sensors. I bought several small wooden boxes to try for size, shape, and general ergonomic-ness when holding, and to enable discussions as to what might be good features and functionality to have in the box.

Our idea was to create a wireless filter box. I wanted to use some of the nrf240l1 radio modules I have acquired as they provide a very cheap mechanism for wireless communication, and there are lots resources available to make them work with Arduino. A detailed tutorial on using Arduino + Nrf24l01 running into Max/MSP software can be found on my website here.

Discussing the box!

We discussed:

The wooden boxes I had purchased and selected a small oval shaped one as the best shape and size to fit in the hand.

Buttons- having some (x2) to enable more functionality- options included click buttons that would provide tactile feedback when depressed or valve style that would more naturally mimic an interaction with an instrument such as a trumpet, like a valve, these would give feedback not as obviously as a click but more suited the instrument paradigm.

Adding a force sensitive resistor (FSR) that could then be pressed harder or softer to achieve some of the effects you would with other instruments such as when fretting a guitar, and allow expression through fingertip movement and pressure of the hand on the box. The mapping of the FSR could then be naturally connected to something like the amplitude of the sound so when pressed harder the sound would be louder, again going with what a player might naturally expect from an interaction of that style.

Light dependent resistor (LDR) this worked well as a mechanism to control some sort of filter, or for example the mute of a trumpet, the cutoff frequency of the sound or the volume. This is taking the movement of the opening and connecting it to any kind of parameter that might need fine movement and can be used to get effects like vibrato and tremolo. A parallel can also be drawn between something like scratching (dj style) by opening and closing the lid, and when connected to a filter controlling some element of feedback, using noise as the sound generator. We had a little play with using the light dependent resistor to control the cutoff frequency on a filter over sounds and using the motion to trigger MIDI notes but felt that the latter did not really play into the strengths of the opening and closing of the box as much as the controlling of an effect.

The aim with the filter box was to create something that when held in a natural position would allow access to the 2 buttons and the FSR as well as facilitating the opening and closing of the lid so that the elements could be used in conjunction with each other and separately in an ergonomic way.

The Pressure Box

We discussed the pressure box and using an array of piezos arranged around the bottom of the circular wooden box to create 8 potential pressure points. The Arduino pro mini we are using in the instruments allows for 8 analogue inputs so would suit this set-up. The box can then be filled with foam and topped with a soft tactile yet spongy material such as neoprene, or potentially some sort of skin stretched over the top in the style of a tambourine and secured down with pins. Being that the piezos are very sensitive to vibration there may be some cross talk between the 8 units but this could provide useful for expression. The sensitivity of the piezos allows for tapping the box to trigger or modulate the sound also.

Future boxes

The hexagonal box though not used yet could potentially feature a new mode of interaction for each of its faces to allow a player to choose their preferred interaction mode and mechanism, this may be one for future exploration.

Next Steps

I will now review what we have discussed and implement them into some more prototypes!

At Dotlib we are always looking for new and interesting ways to interact with sound. We have been developing some ideas for new instruments for the electronic orchestra at Threeways School that allow people to play with sound whilst following a few design rules, what we want is:

A focus on natural interaction, i.e. form affirms function and in this vein we talked about the opening and closing of a box to control a filter
Instruments that do not involve pressing on flat glass like a tablet screen, we want something more tangible
Preferably some local feedback in the form of vibration
Objects that are nice to hold and feel, perhaps finished in wood with a nice varnish like a traditional stringed instrument
As we need to focus on accessibility we need to consider not depending on finger dexterity
We want to provide an instrument that really offers a chance for the player to express them self
We need to tread the line with offering the user control over the creative process, whilst enabling the orchestra as a whole to play cohesively - the real challenge!

We have been looking at a couple of initial ideas for development in terms of the outer casing of the instruments and the inner gubbins that make it work. They are the ‘filter box’ and the ‘pressure box’.

Filter Box

A box that can sense how much it is open and link to a filter in an electronic instrument.

A nice wooden box with a hinged lid that operates very smoothly. We have been looking at what type of box might be suitable and hinges that are robust and pleasing to open, and also what kind of sensor components would give the right kind of response. Thoughts so far include:

LDR (light dependent resistor) on the inside so that as the lid is opened, the amount of light hitting the sensor changes the filter, this is a affordable option as this component is cheap to purchase but the problem comes when trying to calibrate the sensor as ambient light levels can change during a performance and in different environments.
Flex sensor against the inside of the lid so that as the lid is closed the flex sensor is compressed. Flex sensors cost around £7 each so not as affordable as the LDR but does not have to be calibrated as they should always give the same reading. Homemade flex sensors can be made extremely cheaply as seen in this instructable, we have some ready made from a previous project that we will trial in this instrument which follow a similar set-up but use anti-static foam at the centre.
Stretch sensor attached between the bottom and the lid of the box, this would give readings when stretched open and could be used as a nice string to pull the lid closed to give tactile feedback.
Magnet on the lid and hall effect sensor inside so that as the magnet moves away the sensor returns to the base value.

We will have to do some small prototypes to figure out the cheapest and best way to create this box!

Pressure Box

A deformable surface, think tambourine but with a stretchy skin that can then be pushed into to create or manipulate sound. There are a couple of places the inspiration for this has come from, the first is the pads on the Alphasphere and the second is the Firewall. We are still looking to have the wooden outer to hold but perhaps in a circular shape. Options for the sensor include:

Electronic force sensor
Air pressure sensor (this would require a sealed box)
Cheap DIY force sensor
Distance sensor placed underneath the skin

We will be developing and testing from these initial ideas and will connect those blog posts related to that to here so you can keep up to date with the progress on these new instruments for musical expression!