Every guitar player needs a cheap keyboard
Fun fact: I was a synth player before I was a guitar player.
Yes, really. I've literally spent thousands on synths over the years. Everything from the cheap stuff to the ritzy workstations. I was doing pattern sequencing back in the 90s before any guitar players had a clue what that is.
However, these days, I'm perfectly happy with a Casio SA-46 kid's keyboard. And no, I'm not kidding.
While I can get along with a little SA-46, most guitar players need something a little more substantial that has 61 keys on it and more sounds. For that, the Yamaha YPT240 shown above does the job in fine style. It's cheap, it works and it sounds good.
Why have a cheap keyboard?
While I know my way around the piano keys, even if you know next to nothing about synthesizers, there are several good reasons to own a cheap keyboard.
1. Bass sounds
Personally, I prefer the bass guitar (mine is a Yamaha RBX170EW) over synthesized bass on the keyboard. However, there are many, many guitar players who play the bass parts of songs on a synth when songwriting. Keyboard bass always sounds better compared to detuning your guitar or using an octave shifter.
2. String sounds
The string sound on a synth is orchestral strings and not guitar strings. This is a good sound to play along with guitar chords for a bigger, fuller sound.
3. Piano sounds
When a guitar player wants to write a more ballad-like song, having a piano in there is pretty much required, even if it's just simple soft-played chords. Take any piano sound, drench that in reverb and you've got "ballad sound."
To note, piano takes to reverb much better than guitar does. You can pile on the reverb and it sounds fine. Remember, people are used to hearing grand pianos in large rooms where a huge amount of natural reverberation is present by nature.
Remember that adding in effects makes any synth sound better
You can always route your synth through your guitar effects. So if you have delay and chorus pedals, don't be afraid to try those on the keyboard.
A great example of this is this video of the Korg DW-6000 below. The DW-6000 is an old, decidedly crappy synth from 1985. But the add-in of a BOSS RV-5 reverb pedal makes this thing sound like a million bucks:
The DW-6000 sounds awful on its own. But reverb and delay do wonders for synth tones, and the RV-5 makes not only the DW-6000 but any other synth sound great.
Also know that the Yamaha YPT240 linked above sounds 100 times better than the old DW-6000, and it's dirt cheap.
This is me wrangling a Deep Purple style distorted sound out of my SA-46 when routed through my guitar effects:
Yes, even a kid's keyboard can sound that huge.
These are the sounds you simply can't get out of a guitar, which is ultimately why owning a cheap keyboard is so cool.
Remember that you don't have to play using two hands at once
If you only play with one hand, that is OK. Play in whatever style is comfortable, and know that with a multitrack recorder, you can just add in other tracks for other keyboard parts, just like you would with other guitar parts.
If you suck at keyboards, so what? It's a great songwriting tool, it's fun to pluck around on, and it's cheap. Get one.