If you've ever been brave enough to get up and show your talent at an open mic night, you may have wanted just a little help to make your songs really stand out.  For just this reason, I wanted to make my acoustic guitar capable of playing some background accompaniment without any expensive audio equipment or amplifiers.  It can still just be me the guitar and a microphone. 

My idea started while playing with a surface transducer from Sparkfun.  While playing with it, I set it on my guitar to see how it would sound and it came out fairly loud.  I then went to work with an MP3 Trigger and the transducer.

The MP3 trigger was simple double side taped to the bottom of the guitar.  I glued the surface transducer to the inside of the guitar body and simply soldered the transducer leads to the MP3 Trigger.  I put 2 MP3 files on an SD card.  One was the  beginning harmonica for Bruce Springsteen, The River and the second was the harmonica solo in the middle of the song.  When I press the play button I have time to get my hand to the neck and start strumming as the harmonica plays through the sound hole of the guitar.  I plan to get smaller switches near the open frets to do the background switching from a more convenient hand movement.

you can see my video here: