I'm a songwriter who is not terrific at any instrument. I use the piano to find and write the chords. I can't really play the piano more than just hitting a chord on each beat, but I understand it enough to find the chords in the key of what ever song my head came up with. I can play shabby guitar. I try and stay in the keys of G and C and their minors (capo is my friend). I have two strum patterns for 4/4 and one strum pattern for 3/4 & 6/8. It is better for everyone in a public performance if I just sing while someone else plays, even with my own songs. Anyways, I say all this because I want to actually learn to play the guitar well. It's about time. I also would love to know the cello and the penny whistle, but would be happy enough if I actually resolved to get proficient at the guitar.