SchArpeggio-ASchemeMusicArpeggiator

Jeremy Poulin and Mike Stowell
May 2, 2014

Overview

SchArpeggio is a Racket program that allows users to experience dynamic, arpeggiated sound. The program allows a user to enter a custom chord progression with several other options including speed, variable soundfonts, arpeggio motion, and more. The user's configuration is then played back as a dynamic sheet music is drawn.

Screenshot

Jeremy:

Concepts Demonstrated

Mike:

Data abstraction and message passing are used in many objects like the chord-configuration.
String and symbolic manipulation is used to transform user input into something our program can understand.
Notes are drawn using a recursive function.
Heavy use of let statements prevent tedious code repetitions in the drawing program.
Hash tables are kept to perform lookups on notes and their properties.
Lists are utilized to allow easy passing of multiple chord configurations.
Optional arguments allow procedures like that which draws a musical staff behave differently on different input.
Begin is used heavily in the draw-note procedure to allow multiple s-expressions to be evaluated in one if-block.

Jeremy:

Data abstraction and message passing are used to interface with notes objects.
Strings and symbolic manipulation are used to transform user input into options/commands the arpeggiator understands.
Progressions are played in a recursive fashion.
A let statement provides internal variables for the play-chord function.
Hash tables are used to organize both notes and their relative positions.
Lists are manipulated to allow the user to play notes in different orders.
If and cond statements allow configuration for different sounds.
Begin is the foundation of the core functionality for playing multiple notes in the same chord.
A lambda function provides a handle for multi-threading.

External Technology

Mike has made use of the built-in Turtle drawing library while Jeremy worked with the Racket port of SuperCollider 3.

Innovation

Our project is innovative in that it performs two unique tasks at once: it plays back an ear-soothing arpeggio based on a small set of user input while a dynamic sheet music is drawn. The "live" and multi-tasking aspects of this application make it unique in how it behaves. Also it's an arpeggiator in scheme - the first of its kind.

Technology Used Block Diagram

Mike:

Additional Remarks

Jeremy: The real challenge in building an apeggiator in scheme is that the SuperCollider port provides only a subset of SuperCollider's features. The reduces the feasibility of playing song like structures, and forced me to resort to cheap multithreading tricks to play notes. Overall, whilst I don't recommend doing music synthesis in Racket, we've proven it to be possible.

Mike: Drawing musical notes, staves, and symbols is not a simple task utilizing a library that only draws with straight lines and requires you to always keep track of your last drawing movement. Nevertheless, I enjoyed working on this project with Jeremy as it allowed us to explore music in a new light.