A compact text-based format for encoding instrumental music is called MusicXML. It is a widely used format that can be easily parsed and played back by computers. MusicXML allows users to represent the details of a musical score, including notation, pitch, rhythm, and other performance information. It is a popular choice among musicians, composers, and music software developers because of its ability to accurately capture the nuances of a musical score.

Here is a python script that can take a MusicXML file as a command line argument and produce realtime audio output using pygame:

import sys
import music21
import pygame
from pygame.locals import *

# Get the MusicXML file from the command line argument
if len(sys.argv) != 2:
    print('Please provide a MusicXML file as a command line argument')
    sys.exit(1)

music_xml_file = sys.argv[1]

# Convert the MusicXML file to a MIDI file using music21
midi_file = music21.converter.parse(music_xml_file).write('midi')

# Initialize pygame
pygame.init()
pygame.mixer.init()

# Load the MIDI file and play it
pygame.mixer.music.load(midi_file)
pygame.mixer.music.play()

# Wait for the playback to finish before exiting
clock = pygame.time.Clock()
while pygame.mixer.music.get_busy():
    clock.tick(30)

The script first imports the necessary modules and parses the MusicXML file from the command line argument. It then uses themusic21module to convert the MusicXML file to a MIDI file.

Next, it initializespygameand loads the MIDI file usingpygame.mixer.music.load(). It then plays the MIDI file usingpygame.mixer.music.play().

Finally, the script waits for the playback to finish before exiting usingpygame.time.Clock().tick()`. This ensures that the script does not exit until the audio playback is complete.