Hans Memling (1433-1494), part of Christ Surrounded by Musician Angels. Altarpiece of Santa Maria la Real de Nájera (Spain)
The portative dates from the 12th century. It was an instrument for minstrels, or as part of instrumental ensembles, in the time of harps, lutes, fiddles and flutes. The small organ (with one bellow and pipes of metal or wood) would be carried on a belt to use whilst walking. One hand played the keys whilst the other hand manipulated the bellow. It was also possible to play sitting or kneeling.
The portative had several mechanical challenges:
1 a single bellow forced pauses for 'breathing', as you would when singing
2 heavy wooden or metal pipes would add weight to the instrument
3 horizontal placement of the keys
Leonardo da Vinci added astonishing changes to the instrument, as is described in "Codex Madrid II , Fol 76r".
By constructing two parallel vertical bellows, there was a constant air supply. By pushing and pulling a rod, the bellows would be emptied and filled in turn. Moreover, the change speed changed the pressure in the bellows. This way musical expression was improved.
To reduce the weight of the instrument, Leonardo described that the pipes should be made or reinforced paper. This would also reduce the cost of the pipes compared to lead, making the instrument available to a larger group of musicians.
Leonardo da Vinci showed to place the keyboard vertically, 350 years before the invention of the accordion. It made it easier to play and increased the mobility of the musician.