My new app Top Tracks is live on the app store. If you have an Apple Music Subscription, Top Tracks builds Top Forty-style radio stations from Apple Music Playlists.

Now that I've done the marketing thing, let me tell you why I wrote it and give you a better idea of what it does.

It's the early '80s and I'm working as a night time DJ at WDMT, FM 108, an Urban Contemporary radio station in Cleveland.

It's a magic time in radio and WDMT was one of the top stations - it was so popular that in the summer there were neighborhoods you could drive through with your windows down and hear the station playing full volume everywhere.

Each song was on its own cart. A cart was a container that held the music on tape - we didn't have mp3's then, no digital music, heck we weren't even playing music from CDs then.

The cart had a label with the song name, artist name, a bunch of numbers, and a color.

The numbers told us how long the intro was and how many seconds until the post so we could talk over the intro until the post hit. If we worked in the mornings we'd let the post hit and then talk some more. The last number would tell us how long the song is and had an F or C to indicate is the song ended with a fade or ended cold. Who ever put the song onto the cart would also add a magnetic signal to flash at us when the song was about to end.

Radio was so much fun in those days and being an on air personality was just the best.

Anyway, let's get back to those colors.

The songs were divided into categories. There were the top power songs. There were songs that had been power songs but people were starting to fade - I think these were called stay current. There were songs that were moving up but not yet power songs. And then there were the songs that were just being added or were falling down the charts but still deserved being played.

In front of us was a clock with colors that told us what category we should be playing at that position in the clock.

We came out of commercials with a power song so that we could announce a song that was coming up that we knew the audience would stick around for.

At WDMT if the next song was pink then we would reach over to the stack of power songs and play one of the bottom two in the stack. This ensured that the order the songs played in each category would vary.

There were more power songs per hour than the other categories so that the power songs repeated the most often.

The music director would rotate the music and move some of the power songs down, add some new music to the mix, and move other songs up, down or off.

That's what Top Tracks does.

It builds Top Forty stations from Apple Music Playlists. If the playlist is a chart it just takes the song in order of their chart position - if it's not a chart it assigns songs and then watches your song ratings to move a song up or down the next time you choose to rotate the music.

The ratings you give are just a suggestion of whether a song should move up or down - there are other factors. Every time I tap on the heart to rate a song I hear the great Carol Ford saying, "I like that record."

At WDMT we would drop or add songs so that we had a real hour of music within a minute or two. In Top Tracks I don't worry about whether or not a Top Tracks hour is exactly an hour. It won't be.

At 108 we spiced up the regular rotations with songs from the vault every two hours. In Top Tracks I play a song from the gold category once an hour. These songs might rotate anywhere from daily to weekly to even less often.

As long as the playlist has forty songs, the top category in Top Tracks rotates every ninety minutes or so, the next category rotates every 2 1/2 - 3 hours, the next rotates every 3 1/2 - 4 hours, and the bottom category rotates about every six hours.

There were a bunch of things I didn't implement as I wanted to keep the app simple. I may introduce a music directors mode later for people who want more control.

There's a good chance that this app isn't for you or not worth the price - but it transports me back to a magical time in my life and I find myself listening to a lot more music.