Translatin' dem ero mangos

Working my way through Trump's part of Momo-an 24 and I'm stuck on the first page. What the hell does オナニー三味 mean? Masturbation three-string guitar?! I can't seem to kanji IME/Jeffrey's/shitty Japanese grammar knowledge my way through it like I did for Momo-an 21.

Full text box for context here: http://images.4chan.org/jp/src/1294098971609.png

There's a japanese thread you retarded weeaboo faggot