I play the trombone for my school's marching band. Hardest part? There's two, the first one is re-tuning. Because we use our tuning slide to play, we basically have to assume the exact positions of each notes. Every the weather changes by like one degree we have to re-adjust. It's not fun, it really isn't. Second hardest thing is learning other instruments after trombone. The nature of the trombone is distinct and weird to play you're gonna have a hard to learning other instruments, especially if trombone is your first.
I play the violin and I recently took up the piano! Hardest part about the piano is learning to play the bass clef. Hardest part about violin is either containing my rage whenever I play canon in D at a wedding, or sight reading. I’ve been playing violin for 8 years and I still suck at sight reading.
I did piano lessons twice, lost my patience and quit both times. Did cello for two years, got bored and quit. Got a uke about two months ago, I don't play it. I just stare at it and feel guilty because I can't find any time in my day for it.
I practice with my little sister who plays the Baritone and I play it then.. most of the time though I'll steal my friends instruments to play them because why the hell no. Usually it's learning something stupid like Meglovania or Halo theme for no reason.. Yes.. I'm THAT Freshman..