Voice therapy (trans)
Voice therapy or voice training refers to any non-surgical technique used to improve or modify the human voice. Because voice is a gender cue, transsexual women frequently undertake voice therapy as a part of gender transition in order to make their voices sound female, and therefore increase their passability as females in society.  Transgender people and crossdressers who present as women may also desire to feminize their voices and therefore undertake voice therapy.

# Overview
Voice feminization is the desired goal of changing a perceived male sounding voice to a perceived female sounding voice. The term voice feminization is used to describe what the desired outcome of surgical techniques, speech therapy, self-help programs and a general litany of other techniques to acquire a female-sounding voice.  The methods used for voice feminization vary from professional techniques used for vocal training, speech therapy by trained speech pathologists and several Pitch altering surgeries.
Vocal sound is produced by air traveling upwards from the lungs through the opening of the larynx called the glottis where the vocal folds vibrate and phonation or voicing occurs.  The vibrating vocal folds produce a sound that is modified by chambers (like rooms) of the throat and mouth creating resonance frequencies. The size of the chambers directly affects these frequencies. As the size of the chambers increase the deeper (or lower) the formant frequencies become.  These chambers play a very important role in the perception of the timbre (rich, nasal, flat) of the voice. The articulators (tongue, lips, jaw, and soft palate etc.) shape the sound into recognizable speech. Then it is the prosodic features (speaking rate, inflection, pauses) which makes unique speech patterns.
There are several frequencies or harmonics produced at the lips. The fundamental frequency (F0) or the number of times per second that the vocal folds vibrate (in hertz), the conversational fundamental frequency is approximately 200 Hz for adult women and 125 Hz for adult men. Many of the voice feminization techniques, including those of surgeons, focus on the fundamental frequency but do little to address the how the sound is modified by the articulators or prosodic features.  Speech therapists and professional voice coaches offer training in both changing the fundamental frequency and how to change the perception of voice quality.
Voice masculinization is the opposite of voice feminization, being the change of a voice from feminine to masculine. Voice masculinization is not generally required for transsexual men as the masculinising effects of testosterone on the larynx are usually sufficient to produce a masculine voice. 

# Differences between male and female voices

## Physiological
Pitch.: Females usually have higher-pitched voices than males.  Many people believe that this is the only essential difference between male and female voices; however, that is not the case.  The fundamental frequency (F0) of male voices typically ranges from 100 to 150 Hz while ranging from 170 to 220 Hz in females. In a 1988 study in which listeners identified the sex of a speaker by voice alone, all individuals identified as male had an average F0 of 160 Hz or less; all identified as female had an average F0 above 160 Hz.
Resonance, also known as timbre, is another important voice characteristic.  According to Melanie Anne Phillips, resonance is  more significant in "gendering" one's voice than pitch.  One TS woman who raised her average F0 from 110 Hz to 205 Hz over four months was still frequently identified as male on the telephone, which may have been due to the resonance of her voice. However, Anne Lawrence believes that pitch is a more significant gender cue than resonance. An additional factor is the different size of the average vocal tract of males and females.

## Psychological
Like other gendered characteristics, considerable overlap exists between male and female vocal characteristics, especially the psychological ones.
Transsexual women who go through puberty as males will usually develop voices characteristic of males. Hormone therapy does not alter a transwoman's voice once it has masculinized therefore, transwomen who intend to pass as females need to have help with vocal training to feminize their voices.
Vocal training is done formally with the help of several types of professionals and privately by the use of self-help resources including audio or video tapes programs, books, information garnered from websites or chat groups that shares this particular interest. Some transwomen, such as Lynn Conway have feminized their voices with no assistance.
The advantage of going through a speech pathologist instead of many of the other professional that offer training or trying to learn on your own with self-help programs is that  vocal cords can easily become irritated and even develop callous-like growths called vocal fold nodules as the result of incorrect use of the voice and from modifying ones voice too quickly. Individuals who participate in a voice feminization program are trained to self-monitor and become more aware of their vocal quality. They learn to recognize where and how they produce sound, how they are resonating that sound, and how they physically carry themselves and their voice. Related aspects of communication are also addressed including: breathing patterns, gender related non-verbal communication and vocal hygiene.
Some transwomen find voice training to be difficult, while others consider it unnecessary. While most transwomen would prefer to have completely feminine voices, many are unable to achieve this goal.  Some post-transition transwomen have masculine voices, and many have peculiar female voices that may draw attention.
Voice scientists, speech pathologists, language pathologists and ENT physicians (otolaryngology) organize voice production into five components. They are:
- Respiration - power source
- Phonation  - sound source
- Resonance - sound modifier
- Articulation - speech modifier
- Prosody - melodic aspects of speech
In training for a feminine voice, all five components are usually included.

### Things that help make a voice feminine
- Pitch Feminine voices are higher; this may be the most important concern.
- Pitch Range Men tend to be more monotone, varying the pitch helps feminize the voice.
- Speech Rate - Men typically speak at a steady rate, while women tend to speak in shorter bursts followed by pauses.
- Language patterns - The language that women use differs from that of men, although the degree of variation can be quite different from one language to the next (relative to English, it is extremely pronounced in Japanese, for instance).
Tag Questions - Example:  "It's a beautiful day, isn't it?"  A man, on the other hand, would be more likely to simply declare, "It is a beautiful day."
- Tag Questions - Example:  "It's a beautiful day, isn't it?"  A man, on the other hand, would be more likely to simply declare, "It is a beautiful day."
- Supportive environment - As with any skill, speaking with a feminine voice may be easier without the stress of extreme consequences for failure (for example, being identified as a transsexual by someone to whom one is not out.)  Additionally, opportunities to use the feminine voice in conversational situations (as opposed to speech-therapeutic ones) may be helpful in polishing the skill.
NB: These suggestions are based on literature from language and gender scholarship such as Lakoff (1975) and the work of Deborah Tannen. However, this work has been critiqued heavily for representing only stereotypes of how women speak, rather than  how women actually speak, and additionally for representing middle-class white heterosexual women to the exclusion of all others.

# Vocal surgeries
While hormone replacement therapy and gender reassignment surgery can cause a more feminine outward appearance, they do little to alter the pitch or sound of the voice.  The existing vocal structure can be surgically altered using procedures that include
- Cricothyroid approximation (CTA) (is the most common)
- Laryngoplasty
- Thyrohyoid approximation
- Laryngeal reduction surgery (surgical shortening of the vocal cords)
- Laser assisted voice adjustment (LAVA)
While these surgeries exist and can elevate the vocal pitch, there is limited evidence to their overall effectiveness at raising the fundamental frequency over the course of several years.  All of these surgeries have little or no effect on resonce or any other vocal characteristic.  Many in the transsexual community regard voice surgery as inadvisable.  Anecdotal evidence suggests that voice surgery often raises pitch above female norms and that it may result in raspiness, or rarely, complete loss of voice.  Deirdre McCloskey is one transwoman who experienced complications from voice surgery.