python – I am trying to find the frequency of an audio file and then output to a specific target frequency

I am trying to find the frequency of an audio file and then output to a specific target frequency without distorting audio, playback speed and length of song.

This is the code I am using to detect the signal of an audio files frequency:

from scipy.fftpack import fft, fftfreq
import numpy as np
from scipy.io import wavfile
import os


def frequency_spectrum(x, sf):
    """
    Derive frequency spectrum of a signal from time domain
    :param x: signal in the time domain
    :param sf: sampling frequency
    :returns frequencies and their content distribution
    """
    x = x - np.average(x)  # zero-centering

    n = len(x)
    k = np.arange(n)
    tarr = n / float(sf)
    frqarr = k / float(tarr)  # two sides frequency range

    frqarr = frqarr[:n // 2]  # one side frequency range

    x = fft(x) / n  # fft computing and normalization
    x = x[:n // 2]

    return frqarr, abs(x)


def tune_to_frequency(audio_file, target_frequency):
    # Read the audio file
    sr, signal = wavfile.read(audio_file)

    y = signal[:, 0]  # use the first channel (or take their average, alternatively)
    t = np.arange(len(y)) / float(sr)

    # Calculate FFT and frequency spectrum
    frq, X = frequency_spectrum(y, sr)

    # Find the closest frequency bin to the target frequency