I - beginner, can be sorry for the stupid question. Please tell us how and what the guitar signal is converted into MIDI? Sorry for my English!
There are several kinds of MIDI controllers for guitars.
Fishman and Roland make pickups that detect the pitch of the strings played on your electric guitar and turn it into a MIDI signal to drive any MIDI device.
Jam Origin MIDI Guitar is Guitar‑to‑MIDI Software for Mac OS, Windows & iOS.
AC-PAD works a MIDI controller for acoustic guitar.
http://www.acpad.com/
Finally there are lots of pedals that can be controlled by MIDI.
So it depends on what you want to do!
Much obliged to you through!
i respectfully challenge with the answer provided by The MIDI Association. I do not believe the answer goes into the detail the question warrants as all the examples provided have severe limitations.
A controller can be used to control (as with lighting or daw controllers) or convert musical playing into midi data.
The Roland GR-55 is a synthesizer or sound module. A 13 pin (non midi standard) GK series or compatible pickup receives the musical playing. Both devices are needed to convert musical playing into midi data.
The Fishman Triple Play ( http://www.fishman.com/products/series/tripleplay/) has pickup, convertor and data transmitter in one device but the wireless receiver has a USB footprint and requires a computer to operate,
The AC-Pad has controls but can not convert musical playing into midi data.
Casio and Yamaha made several guitar styled product lines that combined pickup, convertor and sound module into the guitar (or guitar like) body. None are currently in production. 🙁 Here's a pretty good overview https://en.wikipedia.org/wiki/Guitar_synthesizer#Guitar-based_models.
Inspired Instruments, Inc. came out with the YouRock midi guitar controller in 2010 and updated it in 2013. It can be used as a game controller or as a midi guitar controller. Here's more about it and the Lineage midi guitar recently added. http://www.yourockguitar.com/21555-2/
I have found the ultimate midi guitar. I have tried it and have one being built for me http://www.industrialradio.com.au/products/solange-6-midi-guitar.html Fully pro guitar and same midi system with some more advanced features as the Industrial Radio midi bass.