Acoustic guitar, yes - absolutely (I use it on a hollow-body electric and it tunes fine without being plugged-in, that's how I always use it). Viola, I wouldn't know, but they do do the same device in an 'all instrument' variant - I'd be very surprised if it doesn't. At the price, these are an absolute steal.
By Orrery on 30 October 2014
You clip it onto the guitar head where the tuning pegs are. Then push the button to turn it on and start playing each string as you would normally tune a guitar and make sure the needle on the screen is in the middle
By Romeo on 04 June 2014
These tuners work on vibration so make sure none of the other strings are vibrating whilst you are tuning up. the low B may be more difficult but be patient and wait until the indicator is in the middle. The Snark SN2 will be the best tuner for you as it is the most accurate.
By Scarborough Music
on 30 September 2016