Just plug your guitar and bass into the normal input socket of the SY-300 with a regular guitar cable. What do you want to do that needs a GK pickup? The GK-3 and GK-3B pickups do NOT use normal 5 pin MIDI cables, the GK pickups use a special 13 pin cable. The SY-300 does NOT have the right type of connection socket for that 13 pin cable. Also, even though many people say the GK-3 and GK-3B pickups are "MIDI pickups", that is INCORRECT. The GK pickups are regular analog pickups that keep the sound of each string separated from the sound of the other strings. The GK pickups do NOT create MIDI information. All the conversion into MIDI information is done INSIDE the GR-55 or SY-1000 pedal units. The GK pickups are just fancy pickups that use a special type of connection cable. EDIT: If you really want the GK pickup capabilities without having to buy another guitar synth unit, you have two main options. 1: Fishman TriplePlay pickup. This is a wireless pickup that does similar things to the Roland GK pickups. Works with electric guitars and bass guitars. It needs a dedicated foot unit or a computer that supports bluetooth wireless connections. A TriplePlay pickup and it's matching foot controller will cost around US$650. If you already have a computer/tablet that supports bluetooth, you could get setup for under US$300. 2: Used Roland GI-10 or GI-20. These are guitar to midi converters. They do not have any internal sounds or effects, they just convert the guitar signal into MIDI. Roland stopped making them years ago so you'll have to look for used ones. A look at online used prices show they currently sell for approx US$300 - $400. Yamaha had a similar guitar to midi converter system called the G50 that works with Roland GK pickups, but even used it sells for approx US$600, almost as much as a new Fishman TriplePlay pickup and foot controller setup. More on reddit.com

The problem with driving DAWs using modern MIDI devices is that it’s all done by USB interface now instead of the 5 pin DIN connectors with which it started. So in addition to a Roland-to-MIDI converter, you need a MIDI-to-USB interface to drive VST plugins in a DAW. More on jazzguitar.be

Has anyone found a cost-effective, improved tracking replacement to the GI-20 ? Thanks. More on pgmusic.com

The truth is they haven’t gotten much better in the last 20 years. Due to the requirement that at least one cycle is necessary to detect pitch, the lower strings in particular suffer from noticeable latency, and even if your playing is extremely precise you end up getting misfired notes all over the place. For live playing, I consider this a non-starter, but even editing MIDI data entered this way afterward is a big pain in the ass. My solution to this (as someone whose brain works better using a guitar, my first instrument) was to find an isomorphic layout MIDI controller which imitates a guitar’s fingerboard. Mine is a custom mechanical keyboard, but these days there are quite a few affordable controllers that support this kind of layout. More on reddit.com