78rpm records

Crackle

Although the standard noise reduction facilities in software such as Audacity or Goldwave can be applied, and may work fairly well on records with a low noise level like the first example above, there are better software tools which cause less distortion. ClickRepair will, as its name suggests remove "clicks" from any digitised gramophone recording (such as those caused by scratches on the record), but also does an excellent job of removing crackle from 78rpm recordings.

In addition, ClickRepair can make best use of the information present in a stereo digitisation of a 78rpm record to produce a mono version. All the following ".mp3" files for examples 1 & 2 are mono (while the above two examples were stereo); this halves the size of files. It should be noted that audio CDs do not have a mono mode, so any tracks that are eventually written to CD have to have identical left and right channels written to the CD-R.

Here are the same two examples after applying ClickRepair with its "Default 78" settings; these settings include stereo→mono.

1.Croen y doafad felan (file size 0.9MB)  2.  start of The Flamborough Sword Dance (file size 0.7MB)

ClickRepair identifies and removes each individual "spike" in the digitised time history whether these be large (for example a click from a scratch on the record), or small (such as a single occurence making up the crackle). As you can hear in the above examples, it does a really superb job!

Surface noise

However, even the first of the preceeding examples still has surface noise. This sounds very similar to that heard on micro-grove records (that is 33rpm LPs and 45rpm records). This noise can be heard in the first of the above examples (after the application of ClickRepair) particularly in quiet passages or before the start of the track. A much greater level of noise remains in the early part of the second example.

Such noise can be reduced considerably using the same software tools as are used to remove "tape hiss" and mains hum from analogue magnetic tape recordings. An explanation of this is given in one of the sections on audio processing. That section explains the process using Goldwave, but very similar facilities are available in Audacity.

Here are the same two examples after also applying the noise reduction facility in Goldwave.

1. Croen y doafad felan  2. start of The Flamborough Sword Dance

Equalization

Except for early gramophone records (which were intended to be be replayed using mechanical rather than electrical sound reproduction systems), the signal recorded on gramophone records have the amplitude of low freqency sounds reduced and/or the amplitude of high frequency sounds increased. Correcting for this during replay is called "equalization". In the mid-1950s a standard was adopted by most companies in Western countries; this is known as RIAA equalization (Recording Industry Association of America). It is used on all 33rpm and 45rpm records issued in the West after the mid-1950s. Electical circuitry in record players and the phono input of amplifiers has this equalization built in.

Unfortunately, prior to the mid-1950s each record company tended to apply its own equalization. Some companies that produced 78rpm records changed the equalization that they applied as technology and knowledge advanced; some companies changed more than once.

We therfore have to remove the RIAA equalization that has been applied during replay and, except for acoutic (that is mechanically recorded) discs, apply a more appropriate equalization. To avoid uneccesary stages it is best to combine these operations, and because the choice of equalization characteristics can become subjective, I prefer to do this after removing crackle and surface noise. A free software tool, Equalizer, is available from the same source as ClickRepair; this comes with a library of equalizations suitable for 78rpm records from a number of companies. Audacity provides a similar facility with a (different) library of equalizations.

Dealing with the first example, which is a HMV record, there is nothing for HMV in the Equalizer library. The article Legacy Recordings EQ gives equalization characteristics that have been identified for many record companies and, where necessary, for several eras. Unfortunately hardly any of the labels on 78rpm records have a date; presumably this is to allow them to argue about when their copyright runs out! For HMV, the article gives characteristics for four different blocks of years; the one for 1946-1954 seems the most likely to apply to this recording. However, it gives two different possible characteristics, with low frequency 'turnover' at either 500Hz or 800Hz. So now we have to fall back on the human ear to decide which to use. Both can be implemented as custom equalizers in the Equalizer software; I called them HMV500 and HMV800. Applying both to example 1 and listening to the results, I preferred HMV500. HMV800 attenuated the high frequency content more so the percussion instrument became almost inaudible.

1. Croen y doafad felan with RIAA equalization removed & HMV500 applied.

The graph on the left shows the resulting amplifications and attenuations that are applied over the frequency range 20Hz to 20,000Hz. Only for very low frequency notes below 100Hz are there any large changes; there is significant amplification if any sound is found at such a low pitch. High pitched sounds are slightly attenuated.

For the second of the above examples, which is from a record issued by Columbia, there is a filter in the Equalizer library, see graph on left. However, the article Legacy Recordings EQ that has already been mentioned gives five different sets of equalization characteristics that have been applied by Columbia. The one provided in the Equalizer library seems to be that for the "1938-most" series rather than that for the "European" series. However. I was satisfied when I listened to the results of applying this equalization to the second example and to other Columbia recordings.

2. start of The Flamborough Sword Dance with RIAA equalization removed & Columbia applied.

It will be seen that the difference between the RIAA and Columbia equalization curves is not large; the required correction reduces high frequency content of the sound slightly and also reduces low frequency content a little, except at extremely low frequencies.

Amplification

A useful step at this stage is to amplify the digital signal to peak at +1.0 or -1.0. Both Goldwave and Audacity provide a simple facility to do this. It should be noted that in some recordings the leading chord played before the start of the music can be the loudest. To avoid having to limit the volume of the remaining music it may be necessary to reduce the relative amplitude of this chord.

Tempo of performance

Having improved the sound quality of 78rpm recordings, attempting to use many of them with current (early 21st century) dancers raises another issue. The tempo at which the music is performed is often faster, sometimes very much faster, than is now customary or even acceptable.

Fortunately there are tools in audio processing software, including both Audacity and Goldwave, which can change the tempo without altering the pitch of the music. Here is an example where the original recording issued by Columbia is played at 136 beats per minute (bpm). The revised version has been slowed to 124bpm, which is still considered to be quite fast for dancing 'The Bishop', and so retains some of the 'urgency' of the original. ClickRepair, Goldwave noise reduction, and Equalizer have been applied before using "Effect" → "Change Tempo" in Audacity.

• The Bishop - original (file size 4.8MB) @136bpm, as recovered from 78rpm record
  The Folk Dance Orchestra
  Columbia DB 1954
• The Bishop - restored & slowed (file size 2.7MB) @124bpm

It should be noted that although this 78rpm recording is labelled as "The Bishop - Folk Dance", the tune being played is "Miss Dolland's Delight" which became associated with this dance in the 20th century.

Duration

Most 78rpm records are 10 inches in diameter, although some 12" diameter records were issued. 10" records have a running time of a few seconds over 3 minutes on each side. This means the number of repeats of a tune that it is possible to fit into one track is limited. The following example has only 5x32 bars and lasts 3 minutes & 5 seconds.

A technique to extend the duration of a folk dance track using Audacity is given in one of the sections on audio processing. This method has been applied (following the usual clean-up of the sound quality described above) to extend this track to 7x32 bars.

• Roxburgh Castle, The Durham Ranger - original (file size 4.5MB) 5x32 bars, as recovered from 78rpm record
  

  Square Dance Band of the EFDSS:

  N & B Fleming-Williams (fiddle, guitar),

  H & D Kennedy (concertina, drum),

  P Shuldham-Shaw (concertina),

  R Robson (double bass),

  S Mason (piano)

  HMV B.9811

  Note the illustrious make-up of this band including Nan Fleming-Williams, Douglas Kennedy, and Pat Shaw.

• Roxburgh Castle, The Durham Ranger - restored & extended (file size 3.1MB) 7x32 bars