A record producer is first and foremost a recording engineer. Working with a record producer is beneficial for any artist who wants to produce the best possible recording possible---a good producer can take a raw recording of guitar, bass, and drums, and turn it into a top 40 hit. A record producer is skilled in setting up instruments and microphones in order to achieve optimum sound output and retrieval. He adjusts EQ (sound quality), reverb, delay and other effects in order to achieve an ideal sound. He is often skilled at mastering songs, as well. This involves putting the final tweaks on recordings, making sure an album's worth of songs sound alike and making sure that songs sound great in any playback situation, from car stereos to MP3 players. In some recording situations, an engineer will facilitate the recording while the record producer acts as an overseer. Other times, a record producer will take the helm for the entirety of the recording process.
A successful record producer with big credits under his belt will most likely have a good ear for music and knows what does and doesn't sound right in a song. A record producer will often help an artist on the arrangement of a song; for example, he might suggest adding an extra chorus at the end of a song or shaving time off a too-long solo. Sometimes, a record producer will contribute to the actual content of a song, fine-tuning a shaky melody for an artist or offering a new one altogether. A record producer can help an artist achieve a more marketable product this way. A record producer is also beneficial in that he acts as a coach in the studio, motivating an artist to perform better.
A successful record producer is well-known in the music industry and most likely has a large network of connections, from record label executives to publishers to promoters. A well-known producer can open doors for an artist she might not be able to open herself. A record producer often acts as an entrepreneur, scouting talent, signing artists, cultivating careers, and writing and recording an artist's songs. A record producer will often shop music around to music industry professionals he knows. Even if the record producer can't do anything directly for the artist, having her name tied to a successful producer can be enough to spark interest from record labels and publishers.