La La Land quickly became an extremely famous movie after its release – considering that the production for the movie spanned nine years, it is not surprising! Loved in particular for its natural ‘musical’ feel, I wanted to take a look at some of the songs within the soundtrack and how they were produced for the movie over this long period of time. To start off – for certain jazz solo songs, the crew simply got the band together and had them mess around, trying to keep an organic feel by using bass, drums, guitars, piano, small brass section, and some orchestral mockups. Since this was separate from the actual production of the movie, the team had to keep separation between the vocals and other elements so they could be easily edited once on set.
A challenge that they encountered with the other tracks was making sure that the sound of the voices and acoustics matched the sound of the dialogues and singing. To help with this, the production crew had to record the dialogue and the singing at the same time in the same place with the same equipment to eliminate differences. In one instance, they had Emma Stone (Mia) during the song ‘Someone in the Crowd’ sing into a lapel mic and a boom mic above her. In another room, the piano was playing with the pianist following a video feed of her singing. Mia was hearing the piano in her earwigs and they got to a point with this method where they could go through the song in the moment of the performance naturally and not for a recording. This method was also used in the soundtrack songs ‘City of Stars’ and ‘Audition.’
Source: https://www.soundonsound.com/techniques/inside-track-la-la-land