Possible Clues:

• 'Much appreciated,' in a txt
• 'Much obliged to a texter,'
• Chatroom show of gratitude
• "I appreciate it," to a texter
• Letters in a Lucas title
• 'The Audience Is Listening' system
• Counterpart of 'pls'
• Letters of appreciation, in a text
• Movie sound system with a signature "Deep Note"
• Appreciation abbreviation