The English preposition to corresponds to several Italian prepositions:
I'm going to the sea — Vado al mare
John came to the rescue – Giovanni è venuto in soccorso
Alice came to repair the car – Alice è venuta per riparare l'auto
Philip is an advisor to the boss — Filippo è un consigliere del capo
Conversely, in order to render the Italian preposition a, you have to use different English constructions, like in the examples you mention.
There's rarely perfect correspondence between prepositions in different languages. Italian da can mean from or by (or also other English prepositions), depending on the context.
In the construction organo a canne, the preposition a introduces a “complemento di mezzo”: “organo che suona per mezzo di canne”. English uses a different rendering: pipe organ is “organ that produces sound by pipes”. Similarly, sedia a rotelle is wheelchair; not so similarly, andare a piedi is “going on foot”.