Play music mixed together with your microphone through skype. Linux only. Uses pulseaudio.

SkypeMusic.py

from pulsectl import Pulse
import os
pulse = Pulse("volume-increaser")

N = 0
for sink in pulse.sink_list():
	print str(N) + " - " + sink.description + " - " + sink.name
	N += 1
mainsink = pulse.sink_list()[int(raw_input("Select your preferred sink... "))]
print "Selected sink: " + str(mainsink)

print ""
print ""
print ""

N = 0
for source in pulse.source_list():
	print str(N) + " - " + source.description + " - " + source.name
	N += 1
mainsource = pulse.source_list()[int(raw_input("Select your preferred source... "))]
print mainsource

print ""
print ""
print ""

print "Creating null0, Only Music..."
cmd = 'pactl load-module module-null-sink sink_name=null0 sink_properties=device.description="OnlyMusic"'
print cmd
os.system(cmd)
print "Created null0."

print "Creating null1, MusicANDMic..."
cmd = 'pactl load-module module-null-sink sink_name=null1 sink_properties=device.description="MusicANDMic"'
print cmd
os.system(cmd)
print "Created null1."

print "Creating loopback from Mic to MusicANDMic..."
cmd = 'pactl load-module module-loopback sink=null1 source=' + mainsource.name
print cmd
os.system(cmd)
print "Created loopback."

print "Creating loopback from JustMusic to Speakers..."
cmd = 'pactl load-module module-loopback sink=' + mainsink.name + ' source=null0.monitor'
print cmd
os.system(cmd)
print "Created loopback."

print "Creating loopback from JustMusic to MusicANDMic..."
cmd = 'pactl load-module module-loopback sink=null1 source=null0.monitor'
print cmd
os.system(cmd)
print "Created loopback."

print "Everything is done... Hopefully..."
print "Run pavucontrol and connect music to JustMusic and set Skype(or other similar service) to record from MusicANDMic."

Mostly based on info from https://xenotoad.net/blog/?p=5.