[Tutor] Chord player
Mr Gerard Kelly
s4027340 at student.uq.edu.au
Thu Jan 8 13:38:34 CET 2009
Actually, I think I can minimize the clipping sound by setting the
sample_rate to be one hundred times the value of the highest frequency
in the chord. But it's still there for the notes underneath. Oh well,
better than nothing!
----- Original Message -----
From: Mr Gerard Kelly <s4027340 at student.uq.edu.au>
Date: Thursday, January 8, 2009 10:12 pm
Subject: [Tutor] Chord player
> I want to thank Emmanuel from the tutor mailing list for showing me a
> piece of code that let me do exactly what I wanted - making Python
> playa chord from a input of frequencies. I only needed to make a few
> adjustments.
>
> The code (below) uses Numeric. Emmanuel said that Numeric is out of
> dateand should be replaced everywhere by numpy. When I do that
> there is no
> error message but the code doesn't play any sound. So I'm keeping
> Numeric in there (although I read somewhere that Python automatically
> converts Numeric to numpy anyway).
>
> I did have one problem, which is when you play a chord, you hear a
> clipping sound every second. I assume that is because of this line:
>
> def sine_array(hz, peak, n_samples = sample_rate):
> #Compute N samples of a sine wave with given frequency and peak
> amplitude (defaults to one second).
> return Numeric.resize(sine_array_onecycle(hz, peak), (n_samples,))
>
> I thought I could get rid of the clipping noise by making it return
> moresamples than just for one second. For instance if I put in
> 2*(n_samples)instead of the default sample_rate value, it might
> make the clipping
> sound come every 2 seconds etc. However, I have found that if I put in
> any other value other than the default value, it cannot calculate. The
> dimensions are wrong or there is a memory problem or something. I'm
> notsure how the resize method works and I was wondering if it is
> actuallypossible to fix this problem this way.
>
> Here's the whole code:
>
>
> ***
>
> import pygame, time, random, Numeric, pygame, pygame.sndarray
> sample_rate = 44100
>
> def sine_array_onecycle(hz, peak):
> #Compute one cycle of an N-Hz sine wave with given peak amplitude
> length = sample_rate / float(hz)
> omega = Numeric.pi * 2 / length
> xvalues = Numeric.arange(int(length)) * omega
> return (peak * Numeric.sin(xvalues)).astype(Numeric.Int16)
>
> def sine_array(hz, peak, n_samples = sample_rate):
> #Compute N samples of a sine wave with given frequency and peak
> amplitude (defaults to one second).
>
> return Numeric.resize(sine_array_onecycle(hz, peak), (n_samples,))
>
> def waves(*chord):
> #Compute the harmonic series for a vector of frequencies
> #Create square-like waves by adding odd-numbered overtones for each
> fundamental tone in the chord
> #the amplitudes of the overtones are inverse to their frequencies.
> h=9
> ot=3
> harmonic=sine_array(chord[0],4096)
> while (ot<h):
> if (ot*chord[0])<(sample_rate/2):
> harmonic=harmonic+(sine_array(chord[0]*ot, 4096/(2*ot)))
> else:
> harmonic=harmonic+0
> ot+=2
> for i in range(1,len(chord)):
> harmonic+=(sine_array(chord[i], 4096))
>
>
> if (ot*chord[i])<(sample_rate/2):
> harmonic=harmonic+(sine_array(chord[i]*ot, 4096/(2*ot)))
> else:
> harmonic=harmonic+0
> ot+=2
> return harmonic
>
> def play_for(sample_array, ms):
> #Play the sample array as a sound for N ms.
> pygame.mixer.pre_init(sample_rate, -16, 1) # 44.1kHz, 16-bit
> signed, mono
> pygame.init()
> sound = pygame.sndarray.make_sound(sample_array)
> sound.play(-1)
> pygame.time.delay(ms)
> sound.stop()
>
> def main():
> #Play a single sine wave, followed by a chord with overtones.
>
> pygame.mixer.pre_init(sample_rate, -16, 1) # 44.1kHz, 16-bit
> signed, mono
> pygame.init()
> play_for(sine_array(440, 4096), 2500)
> play_for(waves(440,550,660,770,880), 5000)
>
>
> if __name__ == '__main__': main()
>
>
> ***
>
> Thanks for having a look!
>
> Gerard.
>
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Gerard Kelly wrote:
> Hi everyone, I'm a python noob but I have an ambitious (for me) goal: I
> want to make a simple program that allows you to hear combinations of
> notes according to a vector of frequencies.
>
> Does anybody know any module that allows you to input a frequency in Hz
> and returns a sound with that frequency, and lets you do that with
> multiple frequencies, so that you can build chords?
The recipe linked below plays sounds composed of a fundamental and a few
harmonics. It requires Pygame and NumPy.
http://osdir.com/ml/culture.people.kragen.hacks/2007-11/msg00000.html
It is out of date, though. I had to change 'Numeric' to 'numpy' and 'Int16'
to 'int16' to get it to work. Moreover NumPy doesn't seem to work with
Python 2.6.
You can also use TkSnack (http://www.speech.kth.se/snack/). Check the
example named 'notescale' that comes with the module: it defines a function
that receives a frequency as an input and plays a sound; there is also a
graphical interface.
Regards,
Emmanuel
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