Hanon: The Virtuoso Pianist – PDF + Interactive Sheet Music

As a rough guide, this is how the difficulty is spread over the first 30 exercises, which are the ones in the player:

Charles-Louis Hanon (1819-1900) was a French piano teacher and composer. In 1873 he published Le pianiste virtuose (The Virtuoso Pianist) in Boulogne, one of the most widely used piano technique books ever since.

The work has three parts. Exercises 1 to 20 are preparatory and build finger strength and independence; 21 to 43 continue with the development of virtuoso technique, including scales and arpeggios; and 44 to 60 are the most demanding, with repeated notes, thirds, octaves and tremolos.

The edition itself says to start each exercise of the first part with the metronome at 60 and to raise it gradually up to 108.

In MIDI & MusicXML Player you will find exercises 1 to 30: practice them with the audio, slow the tempo down and speed it up little by little.

Hanon died in 1900, so the work is in the public domain. The 30 exercises in the player are an original transcription, and the PDF is the G. Schirmer edition from around 1900, also in the public domain, scanned by IMSLP (the International Music Score Library Project).