The man we see playing the violin just before the closing credits of this show (and most other Steven Bochco productions) is Bochco's father. They computer animated a portrait of him to make it appear he's playing the violin.
Before joining the cast as Detective Connie McDowell, 'Charlotte Ross' appeared in the fifth season as the abused wife of a cop suspected by Simone and Russell of killing a prostitute. When 'Andrea Thompson' left the series, producer Steven Bochco remembered Ross and wrote the part of McDowell for her.
The sets on this show of the "New York streets" are on the back lot of Twentieth Century Fox and were originally built for Hello, Dolly! (1969) in 1968. Some location work was actually done in New York City for most of the show's run, mixing specific scenes with general location footage that was used for between-scenes and opening-credits sequences. By the last few seasons, however, the combination of high costs for location filming and the show's reduced ratings meant that 100% of filming was done in Los Angeles.
According to Steven Bochco, Sherry Stringfield asked the producers to release her from her contract after the first season because she said she was not enjoying being a TV actress and wanted to return to New York. Less than a week after being let out of the contract she was hired as a regular cast member for the new TV series ER (1994). However, in his book "True Blue", David Milch said that Sherry's contract-end request came about because she had very little to do - the prominence of Andy Sipowicz's relationship with Sharon Lawrence's DA took all of the story time that was originally intended for scenes between David Caruso and Sherry - and the request was amiably granted, with Milch also stating he was happy when she got a prominent role on ER.
Prior to the show's premiere and immediately afterward there was enormous controversy over what was perceived to be high levels of offensive language and nudity. Many affiliates refused to air the show and several advertisers boycotted it. Steven Bochco negotiated intensely with the network for a certain amount of language and nudity to be allowed. He has said that because of the pressure on the network from this criticism the show would likely not have survived had it not been an instant hit.