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# LastGenre Plugin

The `lastgenre` plugin fetches tags from Last.fm and assigns them as genres to your albums and items.

## Installation

To use the `lastgenre` plugin, first enable it in your configuration (see Using Plugins). Then, install `beets` with `lastgenre` extra

    pip install "beets[lastgenre]"

## Usage

The plugin chooses genres based on a whitelist, meaning that only certain tags can be considered genres. This way, tags like “my favorite music” or “seen live” won’t be considered genres. The plugin ships with a fairly extensive internal whitelist, but you can set your own in the config file using the `whitelist` configuration value or forgo a whitelist altogether by setting the option to `no`.

The genre list file should contain one genre per line. Blank lines are ignored. For the curious, the default genre list is generated by a script that scrapes Wikipedia.

### Canonicalization

The plugin can also canonicalize genres, meaning that more obscure genres can be turned into coarser-grained ones that are present in the whitelist. This works using a tree of nested genre names, represented using YAML, where the leaves of the tree represent the most specific genres.

The most common way to use this would be with a custom whitelist containing only a desired subset of genres. Consider for a example this minimal whitelist:

    rock
    heavy metal
    pop

together with the default genre tree. Then an item that has its genre specified as viking metal would actually be tagged as heavy metal because neither viking metal nor its parent black metal are in the whitelist. It always tries to use the most specific genre that’s available in the whitelist.

The relevant subtree path in the default tree looks like this:

    - rock:
        - heavy metal:
            - black metal:
                - viking metal

Considering that, it’s not very useful to use the default whitelist (which contains about any genre contained in the tree) with canonicalization because nothing would ever be matched to a more generic node since all the specific subgenres are in the whitelist to begin with.

### Genre Source

When looking up genres for albums or individual tracks, you can choose whether to use Last.fm tags on the album, the artist, or the track. For example, you might want all the albums for a certain artist to carry the same genre. The default is “album”. When set to “track”, the plugin will fetch both album-level and track-level genres for your music when importing albums.

### Multiple Genres

By default, the plugin chooses the most popular tag on Last.fm as a genre. If you prefer to use a list of popular genre tags, you can increase the number of the `count` config option.

Lists of up to count genres will then be used instead of single genres. The genres are separated by commas by default, but you can change this with the `separator` config option.

Last.fm provides a popularity factor, a.k.a. weight, for each tag ranging from 100 for the most popular tag down to 0 for the least popular. The plugin uses this weight to discard unpopular tags. The default is to ignore tags with a weight less then 10. You can change this by setting the `min_weight` config option.

### Specific vs. Popular Genres

By default, the plugin sorts genres by popularity. However, you can use the `prefer_specific` option to override this behavior and instead sort genres by specificity, as determined by your whitelist and canonicalization tree.

For instance, say you have both `folk` and `americana` in your whitelist and canonicalization tree and `americana` is a leaf within `folk`. If Last.fm returns both of those tags, lastgenre is going to use the most popular, which is often the most generic (in this case `folk`). By setting `prefer_specific` to true, lastgenre would use `americana` instead.

### Handling pre-populated tags

The `force`, `keep_existing` and `whitelist` options control how pre-existing genres are handled.

As you would assume, setting `force: no` won’t touch pre-existing genre tags and will only fetch new genres for empty tags. When `force` is `yes` the setting of the `whitelist` option (as documented in Usage) applies to any existing or newly fetched genres.

The following configurations are possible:

Setup 1 (default)

Add new last.fm genres when empty. Any present tags stay untouched.

    force: no
    keep_existing: no

Setup 2

Overwrite all. Only fresh last.fm genres remain.

    force: yes
    keep_existing: no

Setup 3

Combine genres in present tags with new ones (be aware of that with an enabled `whitelist` setting, of course some genres might get cleaned up - existing genres take precedence over new ones though. To make sure any existing genres remain, set `whitelist: no`).

    force: yes
    keep_existing: yes

Attention

If `force` is disabled the `keep_existing` option is simply ignored (since `force: no` means `not touching` existing tags anyway).

## Configuration

To configure the plugin, make a `lastgenre:` section in your configuration file. The available options are:

- auto: Fetch genres automatically during import. Default: `yes`.

- canonical: Use a canonicalization tree. Setting this to `yes` will use a built-in tree. You can also set it to a path, like the `whitelist` config value, to use your own tree. Default: `no` (disabled).

- count: Number of genres to fetch. Default: 1

- fallback: A string to use as a fallback genre when no genre is found `or` the original genre is not desired to be kept (`keep_existing: no`). You can use the empty string `''` to reset the genre. Default: None.

- force: By default, lastgenre will fetch new genres for empty tags only, enable this option to always try to fetch new last.fm genres. Enable the `keep_existing` option to combine existing and new genres. (see Handling pre-populated tags). Default: `no`.

- keep_existing: This option alters the `force` behavior. If both `force` and `keep_existing` are enabled, existing genres are combined with new ones. Depending on the `whitelist` setting, existing and new genres are filtered accordingly. To ensure only fresh last.fm genres, disable this option. (see Handling pre-populated tags) Default: `no`.

- min_weight: Minimum popularity factor below which genres are discarded. Default: 10.

- prefer_specific: Sort genres by the most to least specific, rather than most to least popular. Note that this option requires a `canonical` tree, and if not configured it will automatically enable and use the built-in tree. Default: `no`.

- source: Which entity to look up in Last.fm. Can be either `artist`, `album` or `track`. Default: `album`.

- separator: A separator for multiple genres. Default: `', '`.

- whitelist: The filename of a custom genre list, `yes` to use the internal whitelist, or `no` to consider all genres valid. Default: `yes`.

- title_case: Convert the new tags to TitleCase before saving. Default: `yes`.

- extended_debug: Add additional debug logging messages that show what last.fm tags were fetched for tracks, albums and artists. This is done before any canonicalization and whitelist filtering is applied. It’s useful for tuning the plugin’s settings and understanding how it works, but it can be quite verbose. Default: `no`.

## Running Manually

In addition to running automatically on import, the plugin can also be run manually from the command line. Use the command `beet lastgenre [QUERY]` to fetch genres for albums or items matching a certain query.

By default, `beet lastgenre` matches albums. To match individual tracks or singletons, use the `-A` switch: `beet lastgenre -A [QUERY]`.

To preview the changes that would be made without applying them, use the `-p` or `--pretend` flag. This shows which genres would be set but does not write or store any changes.

To disable automatic genre fetching on import, set the `auto` config option to false.