The Beauty of Eb Minor
The key pf Eb minor is extremely accessible on both guitar and piano. Particularly, the pentatonic scale within the key. On a piano, if you played only the black keys you would be playing all of the notes in the Eb minor pentatonic scale. On a guitar, you need to tune down. After, the pentatonic scale sits on 0, 3, 5, 7, 10, and 12. What's notable about this, is that 3,5,7, and 12 are all marked on most guitars. 12 is an octave above E, so usually it has a special marking. All you need to remember are the first three marked frets, and 2 frets back from the special one. Using this information, you can put together a piano and guitar with ease. Whether it's single note parts that harmonize, or chords with a lead, the Eb minor scale is the most straight forward.
Two things I'd like to make clear. First, the key and scale of Eb minor are the same notes. A scale is the order of the notes, and a key is how it's used to actually make music. Meaning, when you practice a key you're playing a scale. Once you write a song with that scale it's then in a key. Second, a pentatonic scale is the notes within a key minus any semitones. The pentatonic scale is very pleasant and easy to play with. On guitar, when you learn the pentatonic shape you can apply to any note. On piano, the Eb minor pentatonic is literally highlighted.
Thank you for reading. I hope this makes sense and you can use it to play or write on piano and guitar better.