This comes from this note from Mr. Zipp:
In chat, Maddy suggested this was a note in response to the note she (the one that Deagol wrote) sent to Mr. Zipp. The note read:Empty House?!: Wiggins quote c.1860. 6 broken strings: Mute them.
So if you match up the two notes, our question about the drawings (sketchy timbre) was answered with "Wiggins quote c.1860." Maddy suggested that this was a musical quote. Doing some research revealed a song written by Thomas "Blind Tom" Wiggins called "Battle of Manassas" which he wrote when he was 12 (1861-ish). This song includes "quotes" of other songs, one of which is "Yankee Doodle."Final check: Sketchy timbre needs clarity: not SM57/58. A4 tuned 15 Hz flat: feedback expected.
You can read about the song here: http://artofthestates.org/cgi-bin/piece.pl?pid=274
And listen to a MIDI version here: http://www.twainquotes.com/BattleofManassas.mid
I think this reference to doodle means the drawings are just that - there's no hidden meaning behind them.