Kevin MacLeod is one of the most heard musicians in the world. I say heard rather than listened to because his work is typically used as the background music in Youtube videos. While there are several reasons for his popularity the biggest is that his songs are available under a creative commons attribution license meaning that people can use the tunes in commercial or non commercial works and the only requirement is he must be credited. This alone makes his work pretty appealing to people who just need music and don't want to have to deal with licensing but his other selling point is that he does evocative instrumental pieces which can be fitted to most anything. Combine these two features with his early adaption of this distribution model and his music is probably approaching the ubiquity of classics like Tchaikovsky's 1812 Overture or Strauss's Blue Danube.
A few of his most used songs are Sneaky Snitch, Scheming Weasel, Fluffing a Duck, and Monkey Spinning Monkey. One of his selling points that maybe isn't the most flattering is that most of it is middling as listening material. It sets a mood and gets out of the way. Most of his music can be found on his website: incompitech.
IRON NODER XV: LAST SECOND BARE BONES IRON NODER FREAKOUT!