Sentence was adjourned on 35-year-old Luke Steele Davis for reports, but a judge warned he could be facing prison.
The musician, of Canterbury Road, pleaded guilty to four offences of sexual activity with a child and five of making indecent photographs of a child.
The case was heard at Maidstone Crown Court
He denied causing or inciting a child to engage in sexual activity and a not guilty verdict was entered.
Maidstone Crown Court heard Davis groped the 14-year-old girl's breasts and bottom while she was at his house for lessons.
Police found 37 child sex abuse images on his computer – one at the highest level of five, one at level four, 18 at level three and 17 at level one.
"He is of good previous character. There is a breach of trust in the sense he was her guitar teacher..." - Louise Oakley, defending
Davis also had 65,000 pornographic images on the computer that were not illegal.
Louise Oakley, defending, said Davis had believed the victim to be aged 15 at the time, but made it clear he knew she was still a child in law.
"This is a case where a pre-sentence report is absolutely essential," said Miss Oakley.
"He is of good previous character. There is a breach of trust in the sense he was her guitar teacher."
Miss Oakley said Davis was still teaching guitar, but lessons were recorded and his father was present.
Adjourning sentence for four weeks, Judge Martin Joy said there should be no unsupervised contact with children.
"You have pleaded guilty to serious sexual offences," he told Davis. "You must understand by adjourning for a pre-sentence report it is not an indication of the nature of the sentence."