What Is Quality Control (QC)?
Quality Control, or QC, is possibly the most important part of the mastering process. It matters whether you are printing CDs, pressing up vinyl or making digital files for streaming. QC is there to make sure your music makes it to the ears of the listeners as you intended, error-free. It is the final checkpoint that confirms your project will translate correctly across streaming services, digital distributors, physical media, and archival systems.
Quality Control for Your Mixes
Every master undergoes a detailed inspection. This includes checking for distortion, pops & clicks, dropouts, clipped inter-sample peaks, unintended noise, phase irregularities, and any structural issues such as incorrect spacing, sequencing, or start-time offsets. I will also listen for mix issues: Does the mix have too much bass? Is the sibilance too aggressive? If there are any issues I will communicate these issues to you before we start and might request a new mix. Getting off on the right foot is critical at this stage.The goal is to confirm that the delivered files match the artistic intent and meet professional technical thresholds.
Quality Control for Streaming, Digital, and CD Release
I listen to the final masters to make sure there are no anomalies or variables that were missed during the mastering process or (gasp!) were introduced during the creation of the masters. This includes pops, clicks, and skips. We also confirm all metadata - that includes the data that is embedded in the files like artist name, song names, collection title, UPC and ISRC codes. We also verify the tops and tails of the songs (beginnings and endings). While printing CDs or making DDP masters are becoming more and more an exception, I still QC and analyze for errors. I will generate MD5 checksums for each file. (A checksum is a number representing the sum total of the characters in the file; it won’t match if there is a change in the file.) The checksums are then used at the receiving end to insure that no errors were introduced during transfers.
While rare, it does happen, and if any errors are found during QC process, the master is corrected and checked again for QC. More artists are releasing for multiple formats and it requires each master be tested for QC. This QC process happens behind the scene that you never see. It’s just an extra step to ensure you are receiving what you are expecting.
Quality Control for Vinyl Release
For vinyl, QC is slightly different. The production of vinyl records involves several mechanical steps. Problems can creep in at any time during these processes. Artists releasing vinyl have two opportunities to check their projects.
Step one after the masters are completed is cutting the lacquers. The cutting engineer can make a test lacquer, better known as an acetate for the client to assess the disc cutting process. Most of my clients preview the record for approval later in the process, however.
Step two is when, the cutting engineer creates the master lacquer which is used in the mechanical processes to the create metal parts used for pressing. If requested, a very short run of test pressings are made and sent to the client to evaluate. It is absolutely essential to listen to the test pressings. After you approve the test pressings, the rest of the records are produced at the plant.
I will QC at every stage of the process and often clients will send me the test pressing for QC, which I am more than happy to review.
Quality Control at the pressing plant
Not all pressing plants will perform quality control on test pressing. That’s why it’s imperative we QC the test pressing. It’s another reason not to use a vinyl manufacturing company that doesn’t have their own press. Historically, we have had better results not using a intermediary in the vinyl pressing process.
Quality Control is a HUMAN process
Although digital tools help with analysis, quality control is ultimately a human process. Algorithms cannot reliably detect every nuance that affects translation, such as subtle crackles masked beneath dense mixes or small inconsistencies that only appear with experienced listening. It is work that only a trained ear can perform with the necessary precision.
The QC process takes place behind the scenes and is part of the service you receive when working with a mastering engineer. The goal is to ensure that every detail is correct before your project enters manufacturing or distribution.
