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: