Direct metal mastering (DMM) is an analog audio disc mastering technique jointly developed by two German companies, Telefunken-Decca (Teldec) and Georg Neumann GmbH, toward the end of the 20th century after having seen the same technology used by RCA Princeton Labs for its SelectaVision videodiscs in the late 1970s.

Records manufactured with this technology are often marked by a "DMM" logo on the outer record sleeve. Many current production high quality pressings, as well as standard production LPs from the 1990s, only indicate its use by inscribing "DMM" in the lead-out groove area of the disc.

Neumann was responsible for manufacturing the actual DMM cutting equipment as part of its VMS80 series lathes.

The advantages of DMM (hard surface material) over acetate lacquer cutting (soft surface material) are both sonic and practical: because of the rigidity of the master disc medium, no groove wall bounce-back effects take place after the cutting has been completed. This preserves the original modulation details in the groove walls much better, especially those involved with sudden fast attacks (transients). The improved transient response, as well as the more linear phase response of DMM improve the overall stability and depth-of-field in the stereo image. In addition, disturbing adjacent groove print-through sounds (groove echoes) are reduced in DMM. Also, there is no need to rush the finalized master disc directly into a refrigerator for groove preservation, as in conventional lacquer disc cutting, before processing the master disc to produce matrices for the pressing of the records. Finally, only one electroplating generation is required to produce stampers, as opposed to three for conventional lacquer masters.

The cutting lathe for DMM engraves the audio signal directly onto a copper-plated master disc, instead of engraving the groove into a lacquer-coated aluminum disc. Examination of early DMM discs revealed what appeared to be a high frequency modulation in the groove, thought to be caused by the use of an ultrasonic carrier tone. In fact, there was no carrier tone and the modulation was simply caused by the vibration (squeal) of the cutter head as it was dragged through the copper disc.

Unlike conventional disc mastering, where the mechanical audio modulation is cut onto a lacquer-coated aluminum disc, DMM cuts straight into metal (copper), utilizing a high frequency carrier system and specialized diamond styli, vibrating at 60 kHz to facilitate the cutting.^{[citation needed]}

The DMM copper master disc can be plated to produce the required number of stampers using the one-step plating process. Rather than having to electroform a master (or "father"), mother and then stampers (the traditional "three-step process"), the DMM copper disc serves as the 'mother". Bypassing the silvering process and two electroforming stages reduces the risk of introducing noise that can be generated in the electroforming (galvanic) process. In cases where hundreds of stampers may be required, the DMM disc is often used as a mandrel to electroform a master and mother, from which many stampers are then made. Chemical passivation of the metal surface of each part precludes "plating," so the parts can be mechanically separated from each other upon removal from the tank.

Since the sale of Neumann to German microphone manufacturer Sennheiser, Neumann no longer produces lathes or supplies parts. Since DMM was introduced at the very end of the vinyl age, only about 30 DMM lathes were ever made, compared to hundreds of lacquer lathes from various manufacturers, and about 10 of them were later converted to be used for conventional lacquer cutting. The lathes in use today are kept operational by independent service consultants, as well as cutting room personnel themselves, often by buying incomplete lathes and stripping them for parts.