AN AX TO GRIND
Author: Dan Katz

The "tree" music file consists of 14 clips of fairly well-known rock guitar
solos, as listed below:

I Believe in a Thing Called Love by The Darkness
November Rain by Guns N Roses
Paranoid Android by Radiohead
Stairway to Heaven by Led Zeppelin
Seven Nation Army by The White Stripes
Hotel California by The Eagles
Smells Like Teen Spirit by Nirvana
While My Guitar Gently Weeps by The Beatles
My Sharona by The Knack
Bohemian Rhapsody by Queen
Sympathy for the Devil by The Rolling Stones
Comfortably Numb by Pink Floyd
Black Hole Sun by Soundgarden
Bulls On Parade by Rage Against The Machine

The trigrams in the "logs" list can be arranged to spell the titles of
these songs in order, with one letter in between each pair:

IBELIEVEINATHINGCALLEDLOVE(D)
NOVEMBERRAIN(I)
PARANOIDANDROID(S)
STAIRWAYTOHEAVEN(T)
sEVENNATIONARMY(O)
HOTELCALIFORNIA(R)
SMELLSLIKETEENSPIRIT(T)
WHILEMYGUITARGENTLYWEEPS(I)
MYSHARONA(O)
BOHEMIANRHAPSODY(N)
SYMPATHYFORTHEDEVIL(B)
COMFORTABLYNUMB(O)
BLACKHOLESUN(X)
BULLSONPARADE

The answer is DISTORTION BOX.