John Tullman: Letective Adventures!

You decide to inspect the posters.
There are about fifteen posters. Almost all of the posters display harmonicas. Most of them say something along the lines of, "I love music!" or "I love harmonicas!" The remaining posters are themed around the TV show "Music Man and the Magic Instruments".
Harmon notices you looking at his posters.
"Look!" He shouts, pointing to his posters themed around "Music Man and the Magic Instruments". "That's my favorite TV show, 'Music Man and the Magic Instruments'. I not going to spoil all of it for you, but the show starts off with a musician who one day finds a secret hideout filled with magic instruments. Using the instruments, he gives magical concerts that are the best in the world! However, the evil Medoka soon threatens to destroy all the music he loves, and he has to use the instruments to save the day!"
You don't feel the need to write down anything about the posters. However, you do so anyway.
"Instrument posters: Most of them are about the love of harmonicas, some are themed around 'Music Man and the Magic Instruments'."
What do you inspect next?