An ordinary metronome has one tempo, and songs have sections. MetroBlocks describes a song as a list of blocks:
- lead-ins, for example two 4-bar count-ins with different click sounds;
- song blocks, each with a name, a number of bars, a tempo, a time signature, a click sound and an optional accent grouping for odd meters, such as 3+3+2.
A colour-coded timeline shows the structure and length of the song and highlights the block that is playing. Click a block to start from it.
Playback uses the Web Audio API. The same song can be rendered offline and saved as a WAV click track. Songs are saved in the browser and can be exported and imported as JSON.
It is a static web app with no server. The interface is in Polish.