These Twelve Progressive Duetts [sic] were written for the slide trumpet by Thomas Harper Snr (1786-1853) and published in his Instructions for the Trumpet in 1835.

Harper suggests the slide trumpet could be effectively pitched in 10 different keys by the addition of crooks (extra lengths of tubing) inserted between the mouthpiece and the main body of the instrument. Consequently, music was often written in C major and the choice of crook(s) changed the key that the listener would hear.

These duets are particularly suitable for use when studying transposition. For example, the first few duets mostly use the notes in the chord of C major and instead of transposing each individual note, it would be more effective to change those notes upwards to the chord of D major, if transposing for trumpet in C from a Bβ trumpet; or if transposing to a trumpet in Bβ from a trumpet in C change all the notes downwards to the chord of Bβ major.

Harper Snr did incorporate some dynamic markings and indications of tempo, but in this edition more have been added to encourage expressive performances of these early Romantic pieces.