import re
regex = r"\\[^\\]*\.([^\\]*)\\[^\\]*$"
x = "Y:\\Path\\sub path\\name_of_folder.microphones.flac24\\trackname01.flac"
match = re.search(regex, x)
if match:
print(match.group(1))
aW1wb3J0IHJlCnJlZ2V4ID0gciJcXFteXFxdKlwuKFteXFxdKilcXFteXFxdKiQiCnggPSAiWTpcXFBhdGhcXHN1YiBwYXRoXFxuYW1lX29mX2ZvbGRlci5taWNyb3Bob25lcy5mbGFjMjRcXHRyYWNrbmFtZTAxLmZsYWMiCm1hdGNoID0gcmUuc2VhcmNoKHJlZ2V4LCB4KQppZiBtYXRjaDoKICAgIHByaW50KG1hdGNoLmdyb3VwKDEpKQ==