Abstract is economical. Key words – Music generation,

Abstract – At present all the various methods  present to generate music are very complex,
they are either based on playing recorded samples of musical instruments that
is high priced and non creative or by synthesis which involves a large number
of components and is very complex to generate tones. Also a synthesizer can be
designed exclusively for only a single musical instrument. This paper provides
an overview of how the sound of various musical instruments can be generated using
an ARM Microcontroller and a simple binary weighted resistor DAC. This work is
based on ARM Cortex – M4F Microcontroller which has low power consumption and
is economical.

     Key words – Music generation,
Musical Instruments, Binary weighted resistor Digital to Analog Convertor, ARM
Cortex M4F Microcontroller.

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I.
INTRODUCTION

Music is an
indispensible part of life for billions of people all over the world. It is an
art and the harmonious creation of voice.1 Objects used to generate sound are
musical instruments. There are primarily two ways of creating music
electronically, Sampling and Synthesis. In Sampling the sound of the musical
instruments are recorded into digital form and then played with modifications
like modulation, looping and phase shifts. Either one or

 

many samples for one
note of a musical instrument are recorded. To play songs on various instruments
expensive libraries of the samples need to be purchased. Music synthesis is a
sub-field of Music Technology. In the field of music synthesizers are the
instruments that are used to generate and record music. Music Synthesizers
replicate traditional musical instruments and can generate new tones that
cannot be played on acoustic instruments. There are various methods by which
synthesizers can generate sounds such as additive, subtractive, wavetable,
modulation and sample based synthesis. Current synthesizer are very expensive
and are designed to play a single instrument. They are complex in operation and
consist of numerous components One of the barriers to playing music is the high
cost, bulky size and regular maintenance 
of musical instruments. The basic motive of this work is to develop a
device that can fulfil the need of playing various musical instruments under a
single system. This device is user friendly as a user who does not know
how  to play an instrument can compose
new music or play existing songs. The circuit construction and operation are
very simple and creative music can be composed.

II.
RELATED WORK

Digital Synthesizers use digital signal processing
methods to synthesize the sound of musical instruments. Contrary to Analog
Synthesizers that were constructed using analog circuits and samplers that
simulated the recorded samples of the instruments, digital synthesizers
generate a sequence of sampled numbers converted from an analog waveform. The
first digital synthesizer prototype developed by Yamaha2.They constructed it
based on John Chownings FM Synthesis algorithms with many up gradations to
avoid distortions. K.Balasubramanian proposed 
a music synthesizer which was is based on creating sound patterns of
musical instruments by recurring occurrences of its fundamental sound signal.3
The frequency of the notes could be programmed. The instrument playing was also
displayed on a 16-segment device. Currently digital synthesizers are completely
based on software, “softsynth” 
which is a program for generating music signals.

×         
.

METHODOLOGY/IMPLEMENTATION

Each musical instrument
has a unique waveform, a sequence of numbers that generate this waveform is
stored as an array and is sent to the DAC. The DAC output produces the wave by
playing it depending on the frequency inputted. Each note of a song is played
for a duration specified by the user. This circuit is implemented using a
simple binary weighted resistor DAC. Higher order DACs can be used to improve
quality of the sound produced as more number of samples for amplitude are
selected. The number of various musical instruments that can be played is
determined by the DAC.A 4 bit binary weighted resistor DAC can play 4 different
instruments and an 8 bit DAC can play 8 different instruments.

Push buttons correspond
to each musical instrument. For a given 
set of notes entered by the user the song starts to play when the button
is pressed. The main program contains the complete list of notes for a particular
song. The digital numbers fed to the DAC is converted to produce a wave similar
to that particular instrument and with the help of Systick Timer that wave is
produced multiple times depending on frequency of the musical note to generate
music. The software code is executed on a microcontroller development tool/ (Embedded
Development Tool) Keil uVision4  and
is written in the C programming language.

Implementation of GUI

Graphical User
interface portrays a diagrammatic illustration and is easy to interact with for
users. The work was  implemented on
MATLAB and a GUI(Graphical User Interface) was created to play music of
different instruments.

 

RESULTS

The Fig(1) is the
circuit of the implemented work. It consists of four switches to play four
different instruments and a 4 bit binary weighted resistor DAC connected to the
Microcontroller.Fig(2), shows the 
waveforms with marked sample values 
of different musical instruments that is used to generate the tone of a
particular instrument.

Fig (3) shows the GUI
which plays a song for two different instruments using the harmonic equations
for that particular instrument. Each note can be programmed by specifying its
frequency and duration to be played. Fig(4) shows the main task window of the
GUI. The waveform of the song playing will be shown on the axes plot and Fig(5)
shows the GUI playing violin song 2 and its corresponding waveform is
generated.

 

CONCLUSION

In this paper, it is
proven that by constructing a circuit with an ARM Microcontroller and DAC
circuit a system could be developed to play various musical instruments in an
economical and simple manner.

Presently, the
project implemented can play one instrument at a time, this limitation can be
overcome by utilization of the other timers or the ARM microcontroller to play
more than one instrument simultaneously. The implementation on MATLAB can be
extended to many musical instruments by using its respective harmonic
equations. 

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