Doxory?

melike: Let's say, hypothetically, that I'd like to learn a new instrument. (currently I know piano and voice.)

Asked 341 days ago

guitar

trs
Guitar + singing
Ian
the viola or cello might be more challenging since you'll have to put your fingers in more or less the exact right spot, whereas on a guitar the frets help you out. but if you're up for it, i find violas and cellos more melodic.
Snarius
Consider the ukelele.
cshiley
Any brilliant advice would certainly be appreciated. Shameless advocacy is often good, too.
Rolando
Any brilliant advice would certainly be appreciated. Shameless advocacy is often good, too.
geoff
Any brilliant advice would certainly be appreciated. Shameless advocacy is often good, too.
plaquette
guitar, to sing and play in the same time
ianyh
Any brilliant advice would certainly be appreciated. Shameless advocacy is often good, too.
snobiwan
It's a shorter-term payoff... a fretted instrument is less of a challenge for an adult to learn (with proficiency)
ternus
Any brilliant advice would certainly be appreciated. Shameless advocacy is often good, too.
khoopes
Any brilliant advice would certainly be appreciated. Shameless advocacy is often good, too.

kevinr, niekie, perturbed, dzm, quince, ZaTyrn, Latty, jgadgil, InquiringMind

viola or cello

lakmiseiru
Cello is so beautiful, and from what music I recall you writing will probably help your composing as well. Viola is nice too, but I think there's more solo opportunities/music for cello.
photon
viola!
charmbr
Depends on types of music and who you might want to play with. Personally, Cello is a favorite of mine, but guitar would definitely be cheaper and much easier to make sound decent in the short-term.
jtf
Any brilliant advice would certainly be appreciated. Shameless advocacy is often good, too.
Yoyo
Cello! I might be biased though.

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Skipped (with comments)

kelseyg
Cello is one of the most beautiful instruments, but do you have the time to get good? It will be much harder but more rewarding than guitar. If you don't want to spend as much on lessons and upkeep do guitar, it'll go well with your voice.

If you make a stupid choice because a website tells you to, it's your own damn fault.