Any musician worth his/her credit knows that accurate tuning is a given. It's a crucial starting point to playing any instrument at home, on the job, in the studio, or on the road, and an embarrassment when it isn't.

Some time ago I was doing an unplugged acoustic gig when my regular stomp box tuner broke down mid-rehearsal. I was in desperate need of a reliable tuner, without a music store in sight. Roll on Agile Partners Guitar Toolkit [iTunes link] for the iPhone/iPod Touch at £5.99

I had heard about various tuner apps on the App Store, but I was reluctant to try any of them. I could not believe that a tuner on my phone would provide the same accurate and reliable tuning that my current (expensive) tuners could. However, I was desperate, so I took the plunge.

Utilizing the iPhone's built in microphone (or the iPod Touch with a microphone headset), Guitar Toolkit's chromatic tuner performed just like using any other quality tuner. It was simple, effective and to my delight, it got the job done.

After the gig, upon further inspection, I soon realized that there was much more than just a common guitar tuner in this app.

Guitar Toolkit comprises a chromatic tuner, a metronome, a chord section, and a scale section too (practice your scales!!).

The chromatic tuner can be used to tune a variety of stringed instruments. By changing the 'mode' selector on the tuner, from standard 6-string EADGBE guitar tuning to 'all notes' tuning, you'll be able to tune almost any musical instrument. Or, you can preselect a particular stringed instrument, from a custom list, for that instruments specific tuning arrangement (guitar, bass, banjo, mandolin, etcetera).

If you're feeling creative, why not come up with your own custom tuning arrangement and input it into the tuner for later reference, or choose one from the alternate guitar tuning selection. DADGAD anyone?

For advanced tuning, you can alter the standard reference pitch from 440.0 Hz to whatever you'd like (some orchestras play at varying reference pitches). I've used it to tune a violin perfectly, and for all you bass players Guitar Toolkit, using the iPhone's microphone, picks up those low notes as well.

There are a few noticeable nice touches here and there. On the tuner, there is the option to alter the display to a 'high contrast mode' for tuning in low ambient light conditions. Also, when the app is open, the power saving/auto-lock features of the iPhone are disabled so the tuner remains usable until you're finished.

Short of being able to plug an instrument line directly in, I can't find a fault with the the Guitar Toolkit tuner.

Update: The plot thickens: the phone also emits the noise just after recording video, and for a much longer period of time. An Apple discussion thread about the noise is here.

Are dogs unusually attentive to, or angry at, your new iPhone 3G S? The folks over at Boy Genius Report have an inkling as to what might be causing it: when a iPhone 3G S user sends a text message or locks the screen, the phone's speaker (the grille on the bottom left-hand side of the device) emits a high pitched sound for approximately three seconds. Many users corroborate the presence of the sound in the comments of the article.

This is an unusual response to these interactions, and further investigation has not yielded any other function that triggers the sound. To activate the sound with a lock, the phone must first be fully unlocked (waking the phone and putting it back to sleep will not trigger the sound). The phone does not emit the tone when the sound is switched off; likewise, when the volume is low, the sound is barely audible, if at all. To my 22-year old ears the sound is soft even with the volume all the way up, but noticeable once I became aware of it (and now a bit annoying).

Boy Genius Report estimates the sound to be in the 15 kHz range (here's a clip of a similar sound for reference), well within the iPhone's listed range of 20 Hz to 20 kHz. Your personal experience with the sound may vary, as higher pitched sounds become harder to hear as you age. Some users report hearing it loud and clear, while others must hold the speaker right up to their ear to hear it; some don't hear it at all. For this reason, it's hard to say whether the sound is endemic to the phone or an anomaly only occurring in certain devices.

A call to Apple's tech support revealed they had no previous knowledge of this issue. They directed me to do a hard reset (holding down the Home button + the Sleep button for ten seconds) but the sound remained. The representative speculated it was a hardware issue, and recommended I take the phone to my nearest Apple Store to get a replacement. Until then, if a rabid dog attacks me, all I have to do to confuse it is unlock and relock my iPhone (or, send a text message).

Can any of you hear this sound too?