I want to buy a ukulele, as my friend had just gotten a Kamoa Soprano from Hawaii. Just had a few questions about em:

Do all ukuleles have the middle C bass string? Also, is a soprano just as good as getting a concert or tenor size? What are the differences?

Here's the site where I might buy from.

not all have a middle C bass string, it depends on the size (or liking of a tuning)

i have a mitchell mu ukulele and i think it is concert, but tenor is small and can be tuned to the standard uku tuning, bigger uku's can be tuned to many tunings and sound good, you can tune a tenor uku to a different tuning but it's kinda weak sounding since it is small
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