if your songs are topical in the sense that a niche audience might be more interested than the general public, you might try joining forums that cater to that niche audience and posting a link.

For example, if the song is humorous and pertains to the medical profession, you could post the link on humor sites as well as sites that draw medical professionals.

One advantage of appealing to niche groups is that the common interest can help it to spread by word of mouth within that community, because everyone in that group knows somebody else who might find it interesting.

Also, put as many keywords in your description as possible, because that's part of what makes your video show up in random searches.

Put a funny cat in the video.

Post something political. You may alienate half the population, but the other half will spread your message far and wide... especially if it is humorous.

Be awesome. viewers love to forward amazing videos. But, the bar for "amazing" is quite high these days...

https://www.dropbox.com/sh/ey71h8ep047758h/AAC12jNM0Hz9Q8zsh5iDeqNHa?dl=0