Merriam Webster defines a musical instrument as "a device (such as a violin, piano, or flute) used to make music."
Sure. But why not a device such as a smartphone, radio or plunger on a garbage can lid? Most people might answer: the smartphone can be used as an instrument with certain apps; the radio plays music for you, so it's not an instrument; you can't make actual music with a plunger and garbage can lid. But wait a minute. Is Jonny Greenwood using a radio as an instrument when Radiohead does "The National Anthem" live? Plunger and garbage can. Not built for the purpose of making music. But "built for the purpose of" isn't in the definition. Can't be used for making music? By who?
Ever heard a song on the radio you didn't like? The fact that you heard it means someone liked it enough to write, perform, record and distribute it. Most people dislike some form of popular music. I dislike lots of it, even when I can see that it's well done. And there's music I love in spite of sloppy performances, out-of-tune vocals and low-quality recordings. Up close, "good" and "bad" seem like relative concepts, not absolutes. If we can accept the ideas that:
- "music" is simply a bunch of sounds grouped together and
- an "instrument" is a device for making sounds,
we quickly discover that our ideas are pretty narrow. Anything and everything can be a musical instrument. Playing the radio is just as valid as playing the saxophone. For that matter, so is starting up your car to make engine sounds - in fact it's the perfect instrument for that particular sound. I probably wouldn't use a car onstage at a jazz gig, but I wouldn't use a saxophone either. Because I can't play it. Not the instrument's fault.
Instruments are just tools. Some are more sophisticated than others. An advanced user can get more out of a machine with more features, while a newcomer wants something that works right away. Some people love the versatility of Android phones and couldn't live with Apple's restrictions. Others just want to use the thing, not learn to program it. But the tools are always useless without the operator. Being good with an iPhone won't turn you into Steve Jobs; driving a stick won't turn you into Michael Schumacher; anyone with a few thousand dollars can have a Pro Tools studio, yet there's only one Pharrell Williams.
At the end of the day, it still comes down to ability and intent. Ability is learned, intent has to come from within. The world is full of people who can help you develop your own ability, or rent theirs. There are more tools out there than you can ever use. They'll help you get there. Only you can determine where you're going.