This disc rotates at a fixed specific speed, set by the user. Anyone who had to move this tuner around was less inclined to like it because of its size and weight: two record-player-sized cases of 30-40 pounds each. Wind instrument players and repair people liked this tuner because it needed no adjustment to show different notes. (The other discs were all gear-driven off of this one.) Incoming audio was amplified to feed a long neon tube common to all 12 discs. When set at A 4 = 440 Hz the tuning fork produced a 55 Hz signal, which drove the four-pole 1650 RPM synchronous motor to which the A disc was mounted. These weights permitted setting it to different reference frequencies (such as A 4 = 435 Hz), although over a relatively narrow range, perhaps a whole tone. The fork had sliding weights, an adjustment knob, and a dial to show the position of the weights. This tuner had an electrically driven temperature-compensated tuning fork the electrical output of this fork was amplified to run the motor. The gearing between discs was a very close approximation to the 12th root of two ratio. They had 12 strobe discs, driven by one motor. However, these strobes are now mainly collector pieces. The first strobe tuner dates back to 1936 and was originally made by the Conn company it was called the Stroboconn and was produced for approximately 40 years. Some inexpensive LED tuners may drift by as much as ☙ cents. The typical accuracy of these types of tuners is around ☓ cents. Small movements of the needle, or LED, usually represent a tuning error of 1 cent. This is why the needle or display on regular electronic tuners tends to waver when a pitch is played. Background noise from other musicians or harmonic overtones from the musical instrument can impede the electronic tuner from 'locking' onto the input frequency. This means that for non-strobe tuners to be accurate, the tuner must process a number of cycles and use the pitch average to drive its display. As well, this waveform constantly changes. Each instrument produces different ratios of harmonics, which is what makes notes of the same pitch played on different instruments (e.g., an A 440 Hz note played on oboe, violin or electric guitar) sound different. It contains a number of harmonic partials, including the fundamental frequency (which a typical listener perceives as the pitch of the note) and additional 'harmonics' (also called 'partials' or 'overtones'). Most musical instruments generate a fairly complex waveform.
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