Police have spoken to more than 30 female former pupils of Chetham's School of Music who have reported historic sexual abuse.
The investigation is focusing on "a pool of about 10 offenders", Greater Manchester Police said.
The women came forward following the sex abuse trial of the prestigious Manchester school's ex-music director Michael Brewer. Brewer was jailed for six years in March after he was found guilty of indecently assaulting ex-pupil Frances Andrade, 48, when she was 14 and 15.
Mrs Andrade killed herself at her home in Guildford, Surrey, a week after giving evidence against him.
The trial heard allegations that sexual activity between teachers and pupils at Chetham's was not uncommon.
Police have made one arrest so far as part of their probe which was launched in February. Former Chetham's violin teacher Wen Zhou Li, 57, now a professor at the Royal Northern College of Music (RNCM), was held in February on suspicion of rape and is on bail pending further inquiries.
Detective Chief Inspector Jamie Daniels, from GMP's Protective Services Division, said: "This is a significant inquiry in terms of potential number of offenders and number of victims.
"We are supporting each and every person who has come forward and made a complaint to us as best we can and I must credit them all for having the courage to face demons that have been haunting them for many, many years.
"This has been a high-profile investigation from the off and due to the complexities and sensitivities involved cannot and will not be rushed. I want to reassure the public that I am absolutely committed to getting justice for these women, many of whom have been spurred on by the bravery shown by Frances Andrade in the case against former teacher Michael Brewer."
"Chetham's and other establishments have and continue to provide help and support at what is clearly a very difficult time for their respective staff and pupils. It goes without saying that if anyone has been a victim of any offence or has any information that can assist this investigation I would urge them to get in touch."