Finding 32-bit WAV audio files on Linux

I was trying to find a way to search my archive of recordings on Linux and return the filenames of 32-bit WAV audio files. It’s a little tricky, but I did it. You’ll need to install the ffprobe command (part of the ffmpeg package).

I came up with this command. It’s quite long and maybe not the most efficient way, but it works!

find . -name '*.wav' -exec ffprobe -i '{}' 2>&1 ; | egrep 'Input|Stream' | grep pcm_f32 -B1 | grep ^Input | awk -F "'" '{print $2}'

eBay Verified Rights Owner (VeRO) Program

This week, I had a clear out of some of my audio equipment and listed an Eagle G148 microphone for sale on eBay.

eBay listing
eBay listing

Within hours, the listing had been taken down by eBay and I was sent this message:

Takedown notice
Takedown notice
Your listing has been removed: Trademark Violation – Unauthorized Item

Hello dj_judas21,After reviewing your eBay account, we’ve taken the following action:
– Violating listings have been removed. A list of items that were removed can be viewed at the bottom of this message.
– We have credited all associated fees except for the final value fee for your listing(s).

Your listing was removed after the rights owner notified us that your item infringes on their trademark rights. We urge you to contact the rights owner directly for more information about why they requested the removal of your listing and whether you may relist the item.

For more information on our VeRO program, go to:

If you have more questions, contact our policy experts:

Please be sure your current and future listings follow these guidelines, keeping in mind that additional violations could result in the suspension of your account.

The rights owner or an agent authorized to act on behalf of the rights owner, Shure, Inc., notified eBay that this listing violates intellectual property rights. When eBay receives a report of this type of violation, we remove the listing to comply with the law.

We encourage you to contact Shure, Inc. directly if you have any questions.

You can send an email to:

For more information on how eBay protects Intellectual Property, or for additional information if you believe that your listing has been removed as a result of an error or misidentification, please visit the following Help page:

Here are the listings that were removed:
272508655545 – Eagle G148 Retro Vintage Super Cardioid Dynamic Microphone “Elvis Style”

We appreciate your cooperation.Thanks,

Please don’t reply to this message. It was sent from an address that doesn’t accept incoming email.

What things annoyed me most about this is that eBay have acted upon an allegation without properly investigating it and without giving me the right to defend myself. I happen to believe the allegation was made in error as the listing itself is an honest description of an Eagle G148 microphone. No mention of Shure anywhere.

I am also annoyed that eBay don’t care about helping me. I read the links in the email but they just contain bland information about their policies and another note that in case of query, eBay sellers should contact the person who made the complaint. They don’t take responsibility for their “investigation”. Here’s an excerpt from one of eBay’s help pages:

If your listing was reported by a VeRO participant, and you believe that your listing was removed in error, try to contact the rights owner directly. The email we sent you about the removal will include their contact information. If the rights owner agrees that they made a mistake, have them email eBay and we’ll allow you to relist your item.

I am pessimistic that emailing Shure will have any effect, or that I will even get a reply. A private individual emailing some random mailbox in a large corporation, asking them to admit a mistake and email another large corporation? Yeah, right. I decided to humour them, though, and here’s what I sent to Joan Haas at Shure.

To whom it may concern,

I received an email from eBay stating that one of my listings was taken down at the request of Shure Inc on the grounds of an alleged trademark violation / unauthorized item.

The item in question was 272508655545 – Eagle G148 Retro Vintage Super Cardioid Dynamic Microphone “Elvis Style”

I feel that Shure Inc has made an error in this matter, since the product in question is not a Shure product, nor a replica/counterfeit Shure product, nor was it advertised as such. I am therefore confused, and would be grateful if you could explain the reasoning behind the complaint.

I have contacted eBay to dispute the takedown and before they take action they have requested that I contact Shure.

“If your listing was reported by a VeRO participant, and you believe that your listing was removed in error, try to contact the rights owner directly. The email we sent you about the removal will include their contact information. If the rights owner agrees that they made a mistake, have them email eBay and we’ll allow you to relist your item.”

So I would be grateful if you could contact eBay to state that an error was made in this matter. If you are unable to do this, please explain to me why it is that you are unable.

I will be contacting eBay directly to follow up on the matter.


To my surprise, I received a reply after just a day or two:


Your sale on eBay was shut down because the microphone you offered infringes Shure’s registered trademarks in the European Community (CTM) and US covering the microphone design. Certificates for CTM registration 4348348 and US registration 2,163,185 are attached for your reference.

Joan Haas
Legal Assistant

So it seems that Shure have requested that eBay remove my listing because they believe the Eagle G148 microphone infringes one of their trademarks – not that I as an individual have been accused of any wrongdoing. I’m pleased and surprised I actually got a helpful and specific response from them.

I’m not an intellectual property lawyer but the trademark registration seems awfully vague and would describe most microphones made in the 1950s. The trademark only describes the physical appearance of the microphone. I’m certainly not going to hire a lawyer to debate the finer points, and I am prepared to accept that Shure are unwilling to allow infringing products to be sold.

I’m still cross at eBay though, being heavy-handed and unhelpful while handling the case. They sent me a follow-up customer service survey to ask me to rate the interaction. I told them what I thought about the inadequacies of their process.

Photo catch-up

A combination of bad weather, having a toddler and generally being busy has meant I haven’t done much photography recently. When I have taken pictures, it’s never been enough to finish a film. Last fortnight, though, I finished a roll of film in my Canon T90 that’s been in there for ages, and I had the inspiration to shoot a few frames of large format film in my Horseman 45HD.

Click on the photos and go through the gallery – I’ve put more detailed captions on the individual photos.

Spem in alium: a motet for 40 synthesizers

Spem in alium was written by Thomas Tallis in c1570 and stands apart from most other choral music because it is written for 40 parts. Most choral music, regardless of the number of people in the choir, only has 4-6 parts. Just for its sheer flamboyance, Spem is famed among choristers due to the challenges of learning and performing it.

Delving into the details of how the music is constructed, rather than being written for a single choir of 40 voices, it is written for eight choirs each of five voices. Each choir comprises one soprano, one alto and either two tenors and one baritone, or one tenor and two baritones.

I decided it would be fun to experiment with recording it, although I don’t currently have access to a choir of 40 with the time to learn and perform it! I thought about William Orbit‘s recording of Barber’s Adagio for Strings and how well the gentle synthesised sounds worked for him. I’m no expert at electronic music but it is something I have played with in the past.

My goals were:

  1. Synthesise the choral parts for Spem
  2. Master the recording to be played back in a 5.1 surround-sound format

Being out of copyright, it was easy (and legal!) to obtain a MIDI file of Spem which contains the 40 parts as separate tracks. I imported it into my favourite musical editor, MuseScore, and had a look at the tracks.

Spem - first 15 bars for the first 15 voices
Spem – first 15 bars for the first 15 voices

For those not in the know, MIDI files don’t contain sound but rather are the computerised equivalent of sheet music – they contain instructions about what notes to play. The computer generates the sound during playback by using a soundfont, which contains sound samples. Just like a real font with a text document, you can change the soundfont for a different sound. The default soundfont with MuseScore is reasonably good but the choir sound is lacking. I downloaded a few free soundfonts until I found one with a choir sound that I liked.

As well as using a soundfont to play MIDI files back, MuseScore can generate a WAV or MP3 sound file from the MIDI file. I got MuseScore to export each choral part as a separate sound file, which can then be edited using a multi-track sound editor – in my case, Adobe Audition. I told MuseScore not to add any effects like reverb to the output, as I’ll do that later.

Track mixer
Track mixer

I imported each sound file to a separate track and played back the result. It sounded pretty terrible – obviously the synthesised choir is not very realistic but with the whole thing played back in mono and with no reverb, it was a rowdy wall of noise. As I planned to create a surround-sound version, I needed to create a sound stage with each voice pinpointed in the right position. This is done by positioning each voice at an angle offset, like this:

Track panner
Track panner

Traditionally, when performing Spem, the 40 choristers stand in a semicircular shape around the conductor, grouped in their eight choirs. This is how I configured my first attempt with the 40 singers standing in a semicircle.

It sounded odd. The first voice is the 1st Soprano followed by the 1st Alto which are voices 1 and 2 out of 40. These both come from the extreme left. As the piece evolves, more choirs join in in ascending numerical order which gives the impression of the sound moving from left to right. This diagram shows the eight choirs, each drawn in a different colour. Sopranos are the palest shades and baritones are the darkest,

Choir layout, arranged in sub-choirs
Choir layout, arranged in sub-choirs

I wondered about arranging the voices grouped not in choirs but in parts: into soprano, alto, tenor and baritone. This would mean all the high notes coming from the left and all the low notes from the right, and that would also sound odd.

Choir layout, arranged in parts
Choir layout, arranged in parts

Eventually I decided to sort the voices using a numerical pattern to split up the choirs and the parts so there would be no overall weighting. I made a spreadsheet to work out the ordering, and then spread the 40 voices over the arc, 5 degrees apart with a total spread of 200 degrees – just over a full semicircle.

Choir layout, systematically spread out
Choir layout, systematically spread out

With the positioning set, I applied gentle compression to each individual voice part to limit the dynamic range and then added a surround reverb to the master channel (i.e., after the parts have been mixed). I chose a cathedral reverb for a long duration and a large, swimmy effect.

The final recording was mastered for 5.1 surround but there’s also a stereo version for Internet compatibility.

As a bonus, I’ve also included Spem rendered for more traditional electronic synthesizers, with each of the eight choirs taking on a different synthesized sound.

Last but not least, I thought I’d render a recording of another of my favourite choral pieces, When to the temple Mary went by Johannes Eccard. It was written around the same time as Spem and also sound richer than the average choral motet because it is written for six parts rather than the more common four. I experimented with sounds but didn’t like either the choral or synth takes, so I decided to render it for string sextet. I think it works quite nicely, and if I can ever get my hands on a real string sextet then I will ask them to play it!

Microphone techniques for recording grand piano

There are many methods of recording a grand piano with their various pros and cons which are suitable for different applications. I recently did some experiments to try and figure out the best way of making a stereo recording in a reverberant room (in this case, a church).

This video demonstrates six different methods but it is just an introduction. There is so much more experimentation that can be done by moving the microphones around the room. Techniques demonstrated are XYAB cardioid, AB omni, ORTFMid-Side and Blumlein.

Basic microphone techniques are taken from Bobby Owsinski’s excellent textbook The Recording Engineer’s Handbook. The microphones being used are Sontronics STC-1 and Behringer B-2 Pro. The music is Piano Parchment by Johnny Pearson – better known as the TV theme from All Creatures Great & Small. Huge thanks to tame pianist Matt Timms for tickling the ivories at All Saints Church, Long Ashton.


Since having a baby and giving up astronomy, I’ve not been out much at night. But last week, Ed invited me to go and photograph the industry at Severn Beach in the small hours. There’s a new SITA Severnside energy recovery centre (i.e. burning rubbish to generate electricity) and every night there’s a delivery of rubbish from London by rail that arrives at about 1:30. It has to come after the last passenger train on the Severn Beach line due to the single track. Ed wanted to photograph the Class 66 that was pulling it while I was happy taking more general photos of the scene.

The train arrived at 1:30 as scheduled and then spent another two hours shunting, collecting the empty rubbish wagons from the previous night and delivering the new ones. It was actually quite interesting watching it all happen. It spotted with rain a few times and unfortunately some of these photos were spoiled by water droplets on the lens, and exacerbated by the harsh floodlights.

These pictures were all taken with my Canon AE-1 Program on Ilford FP4+ film, using a Canon FD 85mm f/1.8 lens (portrait shot) and a Canon FD 135mm f/2.8 (landscape shots). The cyano tint was added digitally after scanning the negatives. This week I ordered a cyanotype kit so I plan to start experimenting with real cyanotypes soon. I also took some pictures at Severnside on colour slide film, but I haven’t yet finished the film.

Priory Church of St Mary, Usk

Last week, Matt and I visited the Priory Church of St Mary in Usk, South Wales. Our visit centred around the large pipe organ which boasts three manuals (keyboards) and horizontally-mounted trumpet pipes.

Usk pipe organ
Usk pipe organ

We were both a bit out of practice but I made some recordings anyway. There are mistakes aplenty but these three pieces show some of the sounds this organ can make. Note the opening of the Wedding March, which uses the trumpet. It’s loud enough to hurt your ears when you’re sitting on the organ stool! Another cool sound available is the the trombone pedal stop, which I only use for one note – the final chord of Heav’n and the Earth display.

When I’ve got some more practice in, I plan to return to Usk and record the organ again. It really is a pleasure to play and to listen to.

Gloucester cathedral

Still playing catch-up with the backlog of films! This trip to Gloucester took place weeks ago but I’m extremely pleased with the photography. Many large churches and cathedrals don’t allow tripods so I’m forced to shoot handheld and to use fast Delta 3200 film, which brings its own set of limitations. Gloucester cathedral is welcoming to photographers and tripods are permitted (provided you purchase a photo permit from the gift shop for £3*) so I was able to shoot slower film (Ilford FP4+) and get finer grain in the negatives, with the luxury of being able to set the aperture to my heart’s desire and drag the shutter instead. The range of tones is much smoother and I think these negatives will enlarge really well.

These were all shot with my Mamiya M645 and Mamiya Sekor 35mm f/3.5 N ultra wide angle lens.

* That’s less than the coffee I bought on the way there so I’m more than happy to support the cathedral in this way.

Old Kodaks

I don’t have many Kodaks in my collection but over the last two days I have been given three very old Kodak cameras. I’ve enjoyed doing a little research on these cameras, and here are my notes.

Vest Pocket Autographic (1915-1926)

Kodak Vest Pocket Autographic
Kodak Vest Pocket Autographic

The Vest Pocket cameras were tiny by standards of the day, hardly any larger than a modern digital compact and as the name suggests, able to fit in a shirt pocket. This one is the autographic model, so there is a flap that opens at the back where the photographer can use a metal stylus to write the caption on the negative directly. This requires special autographic film though, which hasn’t been available since 1932. The body is entirely metal and when folded shut, it is tough.

The Vest Pocket camera launched at around the start of the First World War and due to the portability and durability it became known as the soldier’s camera.

My copy is in a sad state. One of the metal struts has snapped meaning it’s not stable when unfolded, and the bellows are completely torn through in several places. There is lots of paint loss on the body which tells me the camera has been well-used. Nonetheless, the lens and shutter are perfectly working. The photographer can choose two shutter speeds and four aperture settings for quite comprehensive exposure control. Focus is fixed.

It takes hard-to-find 127 film but it may be possible to rig it to use a different type of film.

No. 2A Folding Cartridge Hawk-Eye Model B (1926-1934)

Kodak No. 2A Folding Cartridge Hawk-Eye Model B
Kodak No. 2A Folding Cartridge Hawk-Eye Model B

In 1907, Eastman Kodak purchased the Boston Camera Company, who produced Hawk-Eye cameras. After the First World War, the Hawk-Eye line was retained as a premium range. This particular camera has an immaculate lens and shutter although the bellows have some pinholes at the corners which will need to be repaired before the camera can be used. The camera takes 116 film which is hard to find these days, but it should be possible to use readily-available 120 film.

This camera has the same shutter and aperture options as the Vest Pocket but adds four preset bellows positions which correspond to different focal points.

Six-20 Brownie Junior Super Model (1935-1940)

Kodak Six-20 Brownie Junior Super Model
Kodak Six-20 Brownie Junior Super Model

Like most of the entry-level Brownie range, this one is unremarkable. It’s fully working though, and I may well put a roll of film through it for the soft effect from the meniscus lens. Despite being 20 years more advanced than the Vest Pocket, it is a completely dumb camera with no exposure or focus control.