Ring Tone Text Transfer Language

Ring Tone Text Transfer Language (RTTTL), also known as Nokring, was made by Nokia to allow ringtones to be moved to their cellphones.

Specifications
This is an RTTTL ringtone. This one is named Haunted House:

HauntHouse: d=4,o=5,b=108: 2a4, 2e, 2d#, 2b4, 2a4, 2c, 2d, 2a#4, 2e., e, 1f4, 1a4, 1d#, 2e., d, 2c., b4, 1a4, 1p, 2a4, 2e, 2d#, 2b4, 2a4, 2c, 2d, 2a#4, 2e., e, 1f4, 1a4, 1d#, 2e., d, 2c., b4, 1a4

RTTTL has three parts, which are all separated by one colon each. All of them must be there.
 Part 1 - The name of the ringtone, then a comma. This ringtone's name is defined as "HauntHouse" because the name cannot normally be longer than 10 characters or have a colon ":" character. Smart Messaging allows names up to 15 characters in length, and some applications processing RTTTL also do that.
 Part 2 - The settings (here: d=4,o=5,b=108). "d=" says the default duration of a note is that much of a note. For example, "1" means a whole note, "2" means a half note and so on. "o=" says the default octave. "b=" says the tempo in beats per minute.
 Part 3 - The notes. Each note is separated by a comma and shown in this order: the duration, a standard music note (a, b, c, d, e, f or g), and an octave. The default is used if no duration or octave is defined.

RTTTL is defined in a similar way to Music Macro Language, which many early microcomputers have in their BASIC implementations.

 Durations 
These standard musical durations can be used:
 1 - whole note
 2 - half note
 4 - quarter note
 8 - eighth note
 16 - sixteenth note
 32 - thirty-second note

Adding a period (".") character to the end of a note increases the length of the note by half, which can be used to make dotted rhythm patterns.

 Pitch 
These pitches can be used:
 P - rest or pause
 A - A
 A# - A♯ / B♭
 B - B / C♭
 C - C 
 C# - C♯ / D♭
 D - D
 D# - D♯ / E♭
 E - E / F♭
 F - F / E♯
 F# - F♯ / G♭
 G - G
 G# - G♯ / A♭

 Octaves 
RTTTL has 4 octaves, starting from the A below middle C and going up four octaves, because cellphones could not play some tones audibly at the time it was made. These octaves are numbered from lowest pitch to highest pitch from 4 to 7.

The octave should be left out of the note to prevent rests or pauses in the pattern.

References
How do I distinguish a Nokring/RTTTL ringtone from other ringtones?  (Eric Bematchez, about.com)
RTTTL specification document in Backus-Naur notation

Other websites
Library of RTTTL ringtones
Convert RTTTL to other formats 
Specification

Category:Computer file formats
Category:Musical notation