As fans of old delta blues will already know, even two or three strings on a guitar can be too many when belting out soulful music on a guitar-like instrument. Rather than changing the pitch of a long piece of tuned wire with a glass bottle or steel blade though, the FretPen uses technology to offer players three full octaves from just three frets on a real wood neck and a companion iPhone app. Oh, and it's also a pen.

The maple fretboard of the FretPen has the same number of steel frets as the travel-friendly PocketStrings chord shape practice aid that caught our eye at 2012's Winter NAMM, but not nearly as many strings. In fact, the guitar-shaped FretPen only has one short string running between its teeny tuning head and base block.

Behind the wood are electronics to detect finger position and on its gothic black Super Strat body are four directional buttons. The player uses these buttons to select notes on a virtual 12 fret neck with the help of an iOS app and Bluetooth LE. The sound is thrown out of the speaker or headphone jack of the paired iPhone or iPad. The app defaults to play mode, but also includes and learning mode that teaches pocket pickers a few tricks. Users can also add effects, play chords instead of single notes and select either acoustic or electric guitar tones.

The guitar body, which houses an internal battery and micro-USB port for charging, actually detaches from the neck, allowing users to slot a pen tip in its place and write down the score of the music they've just been playing.

The FretPen is currently at the pre-production prototype stage of development and has launched on Kickstarter to get units into the hands of mobile musicians. The first 50 early bird specials have all been snapped up, so backers will need to pledge at least US$119 to add their names to the shipping list, assuming all goes to plan.

Have a look at the pitch video below to see what's on offer.

Update May 5: The creators of the FretPen have canceled the Kickstarter campaign to work on ironing out some issues. Anyone interested in the development of the device can sign up for updates.

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