First of all, i play rhythm guitar in a melodic death metal band. I've currently been writing some riffs and stuff, nothing structured into a song as of yet. However, I wanna know whats easier for everyone out there: writing a rhythm piece and then writing a solo to go over it, or writing a solo and then writing out the rhythm piece. Which one tends to be easier, better sounding, etc for you? I know it could all just be personal preference but then I wanna know why it is your preference if this is so.
It really depends, sometimes I just write a cool lick and then put some cool chords under it, sometimes I just have a riff I really like and try to find a lick that goes along with it.
Just experiment with it, try to find out what key you're in and see if you can find something that sounds good to you.
Current gear:
Carvin CT6M
TC Electronics Dark Matter distortion
Harley Benton 2x12, with Celestion V30s
Laney Ironheart 60w tube amp
usually, for most bands i know, you write the song all out, jam the parts out so you know how its gonna be recorded(like intro, verse, chorus, solo, etc) and then do drums, bass, rhythm guitar, solos, and vocals. solos and vocals are very similar in mixing and are both usually done last because you have to mix the other parts of the song in a way that "makes room" for the vocals and/or solos. so its common for solos to be written around that time too, so you can have the exact rhythm track that the solo will be mixed over. I personally work on my solos while everyone else records their parts. i sometimes even go back and change my solos after vocals are recorded. the only time i write my solos first are when i want harmonies or question/answer type of things. or if i want a specific melody.
It depends for me really.

When dealing with arpeggios i write the solo parts first and then the chords below.

When doing more like scale:ar soloing i often have a rhythm done already that i just sit and improvise over and pick out the best parts.
Fusion and jazz musician, a fan of most music.

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