The moment Percy heard Oli's voice, his fingers left the keyboard. He'd been playing a jaunty tune, not necessarily because he was in a good mood, but because he was going to perform for the first time since the Monster Fiasco and to play only bluesy songs (which more suited his mood) wouldn't be very appropriate. He turned to his roommate to apologetically say, "Thank you. I hope I wasn't disturbing you. I thought I'd cast a sufficiently strong Silencing Charm around the area."
He then noticed what Oliver was wearing. "Did you just wake up?" It was pretty late in the morning, by Percy's standards - after 9:00.