Martin, who was charged with noise pollution and causing injury, wiped away a tear in court Friday but declined to comment as the case wound up. The presiding judge is expected to issue a verdict within two weeks.
For most people, noise pollution would be jet engines roaring overhead late into the night or mechanical jack-hammers pounding ceaselessly in a neighboring building site.
But for Sonia Bosom, it was Martin's practicing on the keyboard in an apartment above her, allegedly five days a week for eight hours at a sitting from 2003 to 2007 that prompted the legal action.
The regional prosecutor became involved when tests by local authorities found that Martin's music repeatedly peaked at up to 10 decibels higher than the 30-decibel limit laid down for musical instruments in the city.
Authorities in Girona asked the family several times to either stop the piano playing or soundproof the room.
Martin's parents became accessories when they carried out soundproofing work twice, but this failed to quell Bosom's complaints.
Nuria Blanes, an environmental scientist at Barcelona's Autonomous University, said noise around 40 decibels "is not very much." A normal conversation produces 55-60 decibels, with noise in a typical Spanish bar reaching 65-70 decibels.
Bosom's lawyer, Tomas Torres, said that it didn't really matter what kind of music was being played, that what mattered was his client had undergone "four years of suffering." Bosom has told the court she now hates pianos so much she can't even stand to see them in movies.
Martin's defense lawyer, Marc Molins Raich, predicted the outcome of the case would in the end "discredit the denouncer."
Defendants who receive sentences of less than two years in Spain generally do not go to jail unless they have previous convictions.