Where the charts come from
The 4,296 charts in Klaviero come from public-domain and Creative Commons sources, most of them engravings from the Mutopia Project, and every number on this site is measured from those charts.
A MIDI keyboard needs Chrome, Edge, Firefox or Opera on a desktop or laptop. Safari and every browser on iPhone and iPad cannot read one. Full requirements.
Most charts start as a Mutopia Project engraving. Mutopia is a volunteer archive of classical sheet music typeset in LilyPond, and each engraving comes with a MIDI file. Klaviero imports that file, works out which piece it is so a work already in the library is not added twice, picks the instrument voice from the track name or Mutopia's own instrument field, and writes a two-hand chart for piano music or a chart with separate parts for everything else. The rest come from a short list of other sources:
| Source | Charts |
|---|---|
| The Mutopia Project, MIDI exported from volunteer LilyPond engravings | 3,928 |
| Bernd Krueger, piano-midi.de, under CC BY-SA 3.0 Germany | 223 |
| Klaviero, generated symphony movements | 70 |
| Klaviero, arrangements composed for the game | 24 |
| BitMidi, Vivaldi's Four Seasons orchestral sequences reduced to two hands | 24 |
| Public-domain sequences, imported | 18 |
| BitMidi, public-domain sequences | 4 |
| Imported sequences | 4 |
| Bunji Hisamori, via lvbeethoven.fr | 1 |
| Total | 4,296 |
Mutopia publishes a licence for every piece. Across the 3,820 Mutopia pieces with a page here:
| Licence | Pieces |
|---|---|
| Public Domain | 1,463 |
| Creative Commons Attribution 2.5 | 278 |
| Creative Commons Attribution 3.0 | 698 |
| Creative Commons Attribution 4.0 | 104 |
| Creative Commons Attribution-ShareAlike 2.0 | 5 |
| Creative Commons Attribution-ShareAlike 2.5 | 110 |
| Creative Commons Attribution-ShareAlike 3.0 | 752 |
| Creative Commons Attribution-ShareAlike 4.0 | 391 |
| Not recorded | 19 |
How the numbers are measured
Every figure on a piece page is computed from the chart's notes by
tools/seo/piece-stats.mjs, and the pages read the result rather than a
typed copy. Across the library that is 2,907,841 notes across 167.7
hours of music.
Every note in the chart. On a chart with several parts, only the part you play: the accompaniment is played for you and is not counted.
From the start of the chart to the end of the last note, rounded down to the second.
The densest 25-second stretch anywhere in the piece. 25 seconds is long enough that one closing chord cannot set the number.
Notes divided by length.
The share of notes in each hand, from the chart's hand marking, or split by pitch, normally at middle C, on a chart with several parts.
The lowest and highest note in the chart. Which pieces fit 61 keys is built on it.
Klaviero's difficulty rubric, worked out from the notes. Tier 1 is one hand, one note at a time. Tier 2 is both hands, one note each. Tier 3 is up to two notes in a hand at once. Tier 4 is bigger chords. Tier 5 is bigger chords with rapid movement: at least three in ten of the seconds that have notes carry eight or more, or one second carries sixteen. A fast line moves a piece up one tier.
The ranked lists are on the hardest pieces, measured and the five tier pages from tier 1 to tier 5. Every piece is on the pieces list, and every composer on the composers list.
What runs where
Klaviero reads your keyboard through the Web MIDI API, which Chrome, Edge, Firefox and Opera support on a desktop. Safari does not support it on any device, and every browser on iPhone and iPad runs on Safari's engine, so none of them can read a MIDI keyboard. On a Mac, use Chrome, Edge or Firefox. To check that your keyboard reaches the browser before you play, use the MIDI keyboard test. If nothing shows up, MIDI keyboard not detected goes through the fixes browser by browser.