How to change continuously the frequency of a sinusoidal sound?

Question

I am using Pygame to render a Sprite in a window and I want to play a sinusoidal sound which frequency depends on the y position of that Sprite. I

Answer 1

I came up with this solution. Change the freq to newfreq and then change the phase like this: newphase = 2*np.pi*t*(freq-newfreq)+phase

import pyaudio
import numpy as np
from time import time

CHANNELS = 2
RATE = 44100

TT = time()
freq = 100
newfreq = 100
phase = 0
def callback(in_data, frame_count, time_info, status):
    global TT,phase,freq,newfreq
    if newfreq != freq:
        phase = 2*np.pi*TT*(freq-newfreq)+phase
        freq=newfreq
    left = (np.sin(phase+2*np.pi*freq*(TT+np.arange(frame_count)/float(RATE))))
    data = np.zeros((left.shape[0]*2,),np.float32)
    data[::2] = left
    data[1::2] = left
    TT+=frame_count/float(RATE)
    return (data, pyaudio.paContinue)

p = pyaudio.PyAudio()

stream = p.open(format=pyaudio.paFloat32,
                channels=CHANNELS,
                rate=RATE,
                output=True,
                stream_callback=callback)

stream.start_stream()
start = time()
try:
    while 1:
        now = time()     
        if now-start>1/24.:
            newfreq=200+np.sin(2*np.pi*1/20.*now)*100 #update the frequency This will depend on y on the future
            print newfreq
        start=now
finally:
    stream.stop_stream()
    stream.close()
    p.terminate()