This is an Android app designed to play on-disk music in a car. It is intended to be used on a dedicated device that is attached to the car dashboard (not held in a hand), and which communicates with a built-in amplifier/receiver using Bluetooth.

I could find nothing that would do this job acceptably. Not an Android/IOS app, not a purpose-built car stereo. Nothing. So, I had to make my own.

The Car Stereo of The People is based on these three principles:

• Metadata should be gleaned from on-disk directory structure, not from in-file tags. This gives a very limited amount of metadata, but it is consistent and easy to maintain. In contrast, in-file tags give large amounts of metadata, but it tends to be inconsistent and mostly useless.

• There are only a handful of simple "play modes", which should be easy to cycle between with one touch. There is no need to provide access to low-level primitives like playlists or a repeat flag.

• There should be a small number of on-screen controls, all of which should be large. Any on-screen information needs to be in large print. The UI should be usable without having to concentrate on it, and hopefully without even needing to look directly at it. It should try to be as easy/safe to use as the preset push buttons on old mechanical car radios.

All music needs to be stored on an SD card in a single directory tree. The top-level of this tree needs to be named "mcotp", and should be at the root level of your SD card.

Each song that is part of an album should be stored in a path like this:

/storage/0000-0000/mcotp/Band Name/#### - Album Name/## - Song Title.ext

(where the #### is a 4-digit year, and the ## is the track number)

If a song is not part of an album then it should be stored like this:

/storage/0000-0000/mcotp/Band Name/#### - Song Title.ext

(where the #### is a 4-digit year)

This app does not support having multiple bands or albums for the same song file. If you really want that, you can simply copy (or symlink) the file into two or more different directories.

This app also does not yet support compilation albums, with different bands for different songs.

There are two buttons on the main screen that control playback. There is a "play/pause" button and a "next" button. That's it.

There are more options for song navigation. If you long-press on the "next song" button, you'll get a pop-up screen with more options for moving backward and forward.

There are four song selection modes, which each use different rules for determining which songs are heard in which order. The modes are turned on and off via three toggle buttons, one showing the band, one the album, and one the year.

Some of these modes have additional "sub-modes" which tweak their behavior. Sub-modes are cycled through by long-pressing on the play/pause button.

Entire-Collection Mode In this mode, songs are randomly selected from the entire music collection. This is the default mode, which is activated when neither of the three toggle buttons are depressed.

There are two additional sub-modes. "Double-Shot Weekend" plays songs in sets of two by the same band. "Block Party Weekend" will occasionally play a number of songs in a row by the same band.

Band Mode In this mode, songs from the same band are randomly selected. This mode is activated by pressing the band toggle button. This will "lock" on whatever band is currently playing (the current song will keep playing). You can switch back to entire-collection mode by pressing the button a second time.

An additional sub-mode will play songs from the band in chronological order.

Album Mode In this mode, songs from the same album are played, in the same order that they appear on the album. This mode is activated by pressing the album toggle button. This will continue playing the current song, and then follow with whatever song comes next on the album (wrapping around to the beginning of the album at the end). Again, if you press this button a second time, it will switch back to entire-collection mode. This mode will automatically shut itself off after all songs from the album have played.

Year Mode In this mode, songs from the same year are randomly selected (from any band/album). This mode is activated and deactivated by pressing the year toggle button.

An additional sub-mode will play songs from the same decade, instead of just a single year.

You can also enter band or album mode for something you are not currently listening to. To do this, long-press on the band or album button and then select your choice from the list. There are buttons on either side of the list to handle quick course/fine scroll changes.

This is a more complicated operation that requires a little bit of attention, so wait until you're at a red light to do this, okay?

1. Rip out your OEM car stereo and throw it in the trash can.
2. Install a simple 12V bluetooth receiver/amplifier in its place. Ideally this will have an analog volume knob and absolutely no other controls.
3. Get a cheap used Android device and install this software onto it.
4. Configure the device to auto-connect to your receiver, and to auto-adjust its brightness.
5. Attach Android device to your dashboard with duct tape.
6. Run a USB charger to your car's cigarette lighter and leave it plugged in.

Why write a custom player? Why not just use something that's already available? Basically, because I could find nothing that works acceptably.

Because they are very expensive. And, the UIs are absolutely terrible -- not just annoying to use, but actually dangerous to use while driving!

Since this is intended to play music files from an SD card, and since I needed a custom-written interface, I cannot use something like an Arduino or custom hardware... at least not easily.

I did consider a Raspberry Pi, but an Android or IOS device has these significant advantages:

• These devices have batteries, and are electrically isolated from the rest of the vehicle. This is important because a car's power is very very noisy (well, at least it is in the kinds of cars I drive). The isolation prevents this noise from being introduced into the audio signal. The car's noisy power line is solely used to charge the battery.
• Audio can be transmitted digitally via Bluetooth instead of by wire, which eliminates any radiated interference from affecting the audio signal.
• The screen can be set to auto-dim based on ambient light, so the screen will always be appropriately bright.
• Touch screen "just works", and doesn't require any calibration.
• The stock UI is designed for touchscreen apps, and no special settings are needed to hide mouse pointers, window manager decoration, etc.

I picked Android over IOS et al because I happen to have an old Android device that was laying around. I only needed to add a simple 12V Bluetooth amplifier, which can be had for very cheap money.

Here are some aspects I find problematic about most currently-available Android players.

When I want to skip forward one song, I want to do it right now. I don't want to have to navigate or scroll anywhere to find the controls. I don't want to have to carefully aim my finger at a tiny button, and then navigate back if my thumb was 4 pixels off. I want a nice big "next" button that I can see out of the corner of my eye and be able to press while still concentrating on driving.

Most existing Android players confine their controls to a tiny area of the screen, and devote the rest of the screen to stuff I don't care about, like grids full of album art, or artist bios, or even ads. It seems that these are geared towards people who, for some reason, want to "interact" with their music visually on a screen. I don't want to do that. I just want to listen to it.

Existing Android players use in-file tags to attempt to organize music metadata.

But, it's a gigantic pain in the neck to try to maintain in-file tags. There are different tag formats, different tag types, and hundreds (thousands?) of different strategies that are used. Tag editing software is cumbersome and not usually effective on all types of music files and tags.

This means that it's difficult to avoid inconsistencies. Here's a small sample of the many problems seen when using existing Android players that use in-file tags:

• Incorrect separations. According to tags, I have music by three totally separate bands named "Echo & the Bunnymen", "Echo and the Bunnymen" and "Echo And The Bunnymen". I also have three totally different Replacements albums, named "Tim", "Tim (1985)", and "Tim (remastered)". Yuck.

• Metadata with negative value. This takes up screen real estate, and adds complexity in navigation, while providing zero benefit. For example, players will try to organize by genre, but...

  • I see a genre called "80s", which has exactly one song in it, even though I have hundreds of albums from the 1980s.
  • Here are some separate genres I see listed: "Country-Rock, Singer/Songwriter, Folk-Rock, AlbumRock", "Country/Rock", "CountryRock", "Album Rock", "Country-Rock, Singer/Songwriter". Each of these has some Neil Young songs in them. There are probably more.
  • Here are some release date tags that are all treated as totally distinct: "1989", "89", "Jan 15, 1989".

• Some songs are associated with "Greatest Hits" albums, while others are associated with their original albums.

• Some songs on the same album are listed with inconsistent track orders (presumably from different CD/vinyl/cassette track ordering).

Some players really really really want me to stream music.

I basically have two choices for how to listen to music:

1. I can use an SD card smaller than my fingernail. On this, I can store like 5000 albums worth of music. Then, I can have all of my music with me everywhere I go, for the rest of my life.

2. I can stream music over the internet, which means I am relying on the following:

• I need to having decent-speed data service any time I want to listen to music. Driving in rural Vermont? No streaming.

• Some crappy tech company needs to have up-to-date licensing agreements in place with all of the (even crappier) multinational rights-owning conglomerates that hold the rights to some of the songs I want to listen to. Someday, Google Play Music will get into a contract dispute with Universal Music Group, and then I won't be able to listen to Paul's Boutique anymore.

• That crappy tech company actually needs to find all the music I want to listen to, and make it available and discoverable. What are the chances that Google Music will have the "Smash Some Pumpkins" single from the The Broken Toys (an 80s hardcore band from Lawrence, Mass)?

The first option is obviously vastly superior. I'd almost need to be insane to choose #2. Yet, every time I open Google Play Music, it brings me to a screen full of streamable stuff instead of to my on-disk collection. I have to waste time navigating away from that every single time.

Here's a situation that comes up often. I'm listening to songs in a random order, and eventually something comes on that I want to listen to more of. Let's say Guadalcanal Diary's "Under The Yoke" comes on, and that makes me want to listen to that whole album.

I would typically have to do something like this in most existing players that I've seen:

• Navigate to a "Library" screen.
• Navigate to an "Artists" tab. This will open at the very beginning of the alphabet.
• Manually scroll all the way down to "Guadalcanal Diary", or else open up a search widget.
• Select the band.
• Find the album "2x4", select it, and click "play".

This is infuriatingly complex to do, even if I'm just sitting in a chair. It is impossible to do safely while driving.

On top of all that inconvenience, it still annoyingly stops playing the current song, and jumps back to the beginning of the album, instead of just continuing to play.

I do understand that music-playing software needs to have concepts like "queues", "playlists", "shuffle", "repeat", and "consume" internally. But, as a user, I rarely care about such things, and I don't usually want to adjust them all independently -- they should normally be hidden away.

For example, there is a difference between "listening to my music collection" and "listening to one specific album". In the former, I want shuffle turned on, but not in the latter. But, I don't want to have to separately adjust multiple options like this all the time.

I've been on this planet almost fifty years, and I don't think I've ever run into a situation where I felt it was appropriate to shuffle a single album. And, yet music players treat "shuffle" as if it were a long-lived user preference to be preserved across all contexts.

In summary, Android/IOS music players are apparently made by people who don't like to listen to music. Purpose-built car stereos are made by people who also don't like music, and in addition aren't particularly good at writing software.