Any musician will know that having both a metronome and a tuner on your phone is a boon - and in this case, although there are tuner UWP apps for Windows 10 Mobile, you don't even need to install anything. MusicKit is a PWA (Progressive Web Application) and runs in the Edge browser. Cool, eh?
Of course, you can turn this into an 'app' yourself with PAWA or just pin it 'as is' on your Start screen. Or just add it as a 'Favourite'. It's up to you. If you're confused by the different PWA options then check out my feature here.
Here's the PWA in action on my IDOL 4 Pro:
A fully working metronome, with audio, and with tap controls to fine tune the tempo (and change the time signature); (right) the tuner, triggering off the phone's microphone (here picking up a very 'sharp' middle C!)
There's a tone generator that didn't actually work on my Alcatel hardware - maybe you'll have more luck on a Lumia? (right) and a Settings/preferences dialog (yes, A4 sometimes needs adjusting if you have older instruments!)