Check out this video for a live demonstration of the instrument, along with the full report I wrote for the course below.

Rose Kitz

Group: Kyle Tomlinson and Ramona Xi

EMID ES95, Prof. Lehrman

12/19/23

Design Goals & Features

Kyle’s frustrations with the physical limitations of the acoustic cello and drums he plays and desire to enhance those acoustic sounds with digital effects inspired this multi-faceted instrument. While imitating the cello and drums in physical form and beginning sounds, we aimed create an instrument that is fun and easy to learn with sonic possibilities beyond acoustic instruments, all in a travel-size form factor while playable by one person alone or a group in a variety of familiar instrument orientations. The simplicity and familiarity of the interface allow anyone to pickup the instrument quickly, while also the variety of sound and musical parameter options enable experienced string instrument or drum players like Kyle to experiment with new sounds without having to learn how to play a completely new instrument.

To meet these design goals, we determined the following features:

Parts for User Interaction

The user interface includes the parts in the image to the right. We chose to combine a wooden body with a white, LED illuminated top, and black & illuminated sensors to communicate our goal of adapting existing acoustic instruments (cello, drums) for expanded & experimental electronic playing.

See the Circuitry/Arduino section for wiring parts & details.

User Interaction Design

The physical form of the Sledgehammer Kablammer imitates string instruments like the cello to achieve a familiar playing interface for users, while sized like a ukulele for easy handling by one person alone (see basic dimensions below). To further enable a variety of playing orientations and multiple players, the instrument has a flat bottom and sides along with a sturdy wooden neck so it can sit on a tabletop or be held upright or sideways, with curved edges for aesthetic and safety.

To add user feedback in a quickly digestible form, the LED strip illuminates the neck and the LCD backlight change to the color associated with the selected instrument sound, as shown to the right.

The LEDs on the neck also ‘follow’ finger position to indicate the pitch selected at any time. For further user feedback, the LCD shows text with the selected instrument sound and scale, updating immediately with the color as the player switches sound & scale.

We admittedly designed the body to our own biases as right-handed players, with pitch change by the left hand and the note-triggering pads to be played by the four right-most right-hand fingers, and the sound-parameter sensors closely & perpendicularly located to be played simultaneously by the right thumb. All sensors were selected to be triggered by a light enough touch so that the instrument takes minimal physical effort to play.

Construction

We fabricated nearly all pieces via laser cutting, as drawn to the right, to achieve the desired flat surfaces and curves (with living hinges), and because laser cutting is a rapid prototyping technique that allows for quick iterations for testing design choices/changes. The tabs on each laser cut piece allow for secure & sturdy assembly.

The only non-exposed fabricated part is the clear sub-top panel, which functions for the FSRs to sit on top of, so that they have a ‘backboard’ to be hit on while being recessed below the top panel — originally, we wanted to include rubber squares on top of the FSRs for a softer playing experience, however the material interfered with FSR performance (and did not look as great as expected), so we decided to keep it simple and eliminate the rubber FSR covers.

However, to achieve a sturdy and smooth neck as well as a pocket for the LED strips to sit within the instrument while diffusing through the top acrylic sheet, we chose to woodwork a 2x4 pine wood bar.

Nearly all electronics are packaged up inside the instrument body, as pictured in the Circuitry/Arduino section, with the exception of:

• Sensor interfaces on the instrument surfaces ➡️ secured tightly to body

• A portion of the LED strip sunk in a pocket of the wooden neck ➡️ covered by white acrylic that is ~30% transparent, the LEDs diffuse to create a glowing effect

• Two power/data cords sticking out of the neck base ➡️ Arduino power from/data to computer, external power for LED strip (avoid overloading Arduino with high-power lights)

Circuitry

The ‘brain’ of the instrument is an Arduino Mega 2560 Rev3, which has 52 digital pins (15 allowing PWM) and 16 digital pins (along with other ports we did not use) to allow for tremendous flexibility for adding sensors and other electronic components.

The main electronic components and their functions are listed below:

To wire each main component to the Arduino and enable proper electrical standards, additional parts are necessary, with connections made either on the breadboard, with alligator clips, or via soldering.

All wiring housed inside of instrument body (image to right) is based on tutorials link in the materials spreadsheet as well as prior knowledge. A specific (clearer) electrical connections diagram is in progress.

Arduino Code

The Arduino functions as the ‘brain’ of the instrument to read and process raw data then send the values over Serial in packs to Max on the USB-connected Mac computer. The code is modular & extendable to allow for easy & quick implementation and testing of new sensors connected to the Arduino. The ‘EDIT THIS’ section at the top has simple arrays of instrument names & light colors, scale names, and electronic component information & names that designers can quickly change, then simply run the code to send to Max over Serial, without having to dive into or understand the nitty-gritty of the code below. The loop-based code takes care of reading, processing, and sending the data for you!

Instrument & color, scale editing

Sensor Changes/Additions

Overall Pseudocode

Below is a pseudocode (high-level, plain English) description of the Arduino (C++) code:

Max Patch

The Max patch translates processed input data from the sensors & Arduino into MIDI notes and parameters, based on the desired logic of the instrument. The main steps are as follows, which run concurrently but are listed in order for simplicity:

See the Appendix for the full Max patch (including Scale and Root Note Switch sub-functions).

Reason Rack

There are 16 modules in the Reason rack, with 15 MIDI channels all on bus A to design the sound for the musical parameters and four instrument options: cello, guitar, ambient, and drums (highlight colors align with LED colors that show when each instrument is selected).

The cello sounds were custom-sampled, clipped & processed in Audacity, and added to Reason by Kyle. The majority of parameters on each Reason patch were left at default, with more adjustments made on the ambient sounds. See the Appendix for screenshots of the full Reason rack.

Changes and Future Directions

The Sledgehammer Kablammer is, by itself, a complete, playable, and fun instrument; no additional changes are necessary, however several improvements could be made: