OAKLAND, Calif. (AP) _ The Oakland Symphony, which had previously canceled its season, has reached a last-minute agreement with striking musicians and will open its season Tuesday, a spokesman said.

''Things happened (Sunday),'' said the spokesman, Herbert Scholder.

At midnight Friday, Scholder had announced that the Oakland Symphony Association had canceled its entire 1985-86 season, which had been scheduled to begin early October.

Before the strike, the average salary for the musicians was $10,076 a year.

Scholder said the new pact covered three years with a change in the third year to a weekly salary instead of wages based on the number of performances or rehearsals by a musician. He would not give further details of the new contract.

The 86 musicians, who were seeking higher wages and schedule changes, went on strike Oct. 3.